In the sense that one is not  re-print of the other, they are not the same,  however, for the example you highlight the difference is 0.4%. As most real meters measure these low resistances to at best a few %, and then one or two flickers of the last digit. So as far as any meter reading is concerned, they are the same. 

There is a large element of "measure with a micrometer, mark in chalk, cut with an axe" about the decision about what is an acceptable Zs level for a given breaker anyway, in the sense it is a very accurate calculation of something that does not happen - for example if faults actually were zero resistance, they would not actually  dissipate any energy and would not get hot - as I'm sure you realise looking at any burnt end will confirm this is not the case ?.


Working the other way, no breaker is made spot on the limit of the breaking range, so when we assume 20 times the rating for a D type, we are being unduly pessimistic, on average one out of the box will be more like 15. But that may vary with batch and the age of the breaker, as the moving parts oxidise and get a bit stiffer.


so 20* 6A is 120A - so to be safe assume no instant break unless the current is >120A , probably similar magnetic parts as a 32A B type.

Then we say what shall we assume about the supply - perhaps 230V and 20% margin for bad luck ? 230/120 is 1.916666  and 20% off for luck is 1.533333 . (when did you last see exactly 230V... )


But should we assume that we are testing cold, but the cable may be hot when the fault occurs, and allow a bit more - and how warm was it when you tested it ? Then during fault, is the CPC already hot as well or just the live cores - probably depends on the arrangement - steel conduit may have a cold CPC, for T and E the CPC is more thermally in contact with the live cores.


Also for the D type some times the thermal part gets there at about the same time as the magnetic, depending on the ambient temperature ,and so maybe we have to assume the breaker is cold and the cable hot.


And now the part of the resistance of the street main, and the real external voltage, will depend on other user's loads, and may change without warning if the DNO needs to change a transformer or make a repair to cables in the street.


My point is not that we need to know all this, usually we cannot hope to, but more that if your design is close to the limit, and relies on a change of less than 5000 parts per million to put it one side of the line or the other, then it does not matter, as the last digits on the tester are about as helpful as a fruit machine. The only safe conclusion is that it is a marginal design, and may or may not meet the advice of BS7671,  depending who tests it and what the weather is on the day, and how clean his meter probes are. A 6A circuit  is unlikely to become immediately  dangerous for want of a few milli-ohms, and there is no need to be alarmed that a slightly different set of assumptions and rounding is not identical.

In the sense that one is not  re-print of the other, they are not the same,  however, for the example you highlight the difference is 0.4%. As most real meters measure these low resistances to at best a few %, and then one or two flickers of the last digit. So as far as any meter reading is concerned, they are the same. 

There is a large element of "measure with a micrometer, mark in chalk, cut with an axe" about the decision about what is an acceptable Zs level for a given breaker anyway, in the sense it is a very accurate calculation of something that does not happen - for example if faults actually were zero resistance, they would not actually  dissipate any energy and would not get hot - as I'm sure you realise looking at any burnt end will confirm this is not the case ?.


Working the other way, no breaker is made spot on the limit of the breaking range, so when we assume 20 times the rating for a D type, we are being unduly pessimistic, on average one out of the box will be more like 15. But that may vary with batch and the age of the breaker, as the moving parts oxidise and get a bit stiffer.


so 20* 6A is 120A - so to be safe assume no instant break unless the current is >120A , probably similar magnetic parts as a 32A B type.

Then we say what shall we assume about the supply - perhaps 230V and 20% margin for bad luck ? 230/120 is 1.916666  and 20% off for luck is 1.533333 . (when did you last see exactly 230V... )


But should we assume that we are testing cold, but the cable may be hot when the fault occurs, and allow a bit more - and how warm was it when you tested it ? Then during fault, is the CPC already hot as well or just the live cores - probably depends on the arrangement - steel conduit may have a cold CPC, for T and E the CPC is more thermally in contact with the live cores.


Also for the D type some times the thermal part gets there at about the same time as the magnetic, depending on the ambient temperature ,and so maybe we have to assume the breaker is cold and the cable hot.


And now the part of the resistance of the street main, and the real external voltage, will depend on other user's loads, and may change without warning if the DNO needs to change a transformer or make a repair to cables in the street.


My point is not that we need to know all this, usually we cannot hope to, but more that if your design is close to the limit, and relies on a change of less than 5000 parts per million to put it one side of the line or the other, then it does not matter, as the last digits on the tester are about as helpful as a fruit machine. The only safe conclusion is that it is a marginal design, and may or may not meet the advice of BS7671,  depending who tests it and what the weather is on the day, and how clean his meter probes are. A 6A circuit  is unlikely to become immediately  dangerous for want of a few milli-ohms, and there is no need to be alarmed that a slightly different set of assumptions and rounding is not identical.