Can Zs at DB ever be less than the Zs of the feeding circuit?

Many thanks for everyone's responses to date on this.

I do not know what they did regarding disconnecting loads etc when they did their tests.  This was actually a medium-size 2-storey church building built over 100 years ago, so not, for example, sprawling over a multi-building site, but has had various extensions and modifications over the years, so may have some structural steel members here and there.  The inspector has acknowledged multiple errors in the report elsewhere, but I was checking if these Zs values were also a bit of a red flag.  There is concern over one particular area of work that he has recommended, which is to replace/upgrade a circuit for reasons that the EICR does not support (a circuit which the inspector says in his observations is only protected by a 32A fuse, but which the EICR clearly says is protected by a 100A fuse). When pushed for clarity, he is now saying 'ah well, that circuit is actually fed from another circuit which is mislabelled'. The whole thing is just a bit fishy, but I am not sure whether to call him out on it or not.  He may be telling the truth, but the EICR (marked unsatisfactory) that he has issued seems to be full of factual/typo errors and I just cannot see that it clearly supports the conclusion that there is a circuit that need upgrading.  If you take the report at face value, as written, it is claiming that connections/circuits exist that just do not exist on the report and which were not recorded on the last inspection report 5 years ago by a different inspector/company. Either his report has failed to record the bad circuits that do exist, or he is recommending to replace circuits that the EICR does not indicate need replacing/upgrading.  On many of the circuits on the EICR, the 'Maximum measured Zs' for an individual circuit bears no resemblance at all to the 'Zs at this board' + the measured R2 for the circuit.

Many thanks for everyone's responses to date on this.

I do not know what they did regarding disconnecting loads etc when they did their tests.  This was actually a medium-size 2-storey church building built over 100 years ago, so not, for example, sprawling over a multi-building site, but has had various extensions and modifications over the years, so may have some structural steel members here and there.  The inspector has acknowledged multiple errors in the report elsewhere, but I was checking if these Zs values were also a bit of a red flag.  There is concern over one particular area of work that he has recommended, which is to replace/upgrade a circuit for reasons that the EICR does not support (a circuit which the inspector says in his observations is only protected by a 32A fuse, but which the EICR clearly says is protected by a 100A fuse). When pushed for clarity, he is now saying 'ah well, that circuit is actually fed from another circuit which is mislabelled'. The whole thing is just a bit fishy, but I am not sure whether to call him out on it or not.  He may be telling the truth, but the EICR (marked unsatisfactory) that he has issued seems to be full of factual/typo errors and I just cannot see that it clearly supports the conclusion that there is a circuit that need upgrading.  If you take the report at face value, as written, it is claiming that connections/circuits exist that just do not exist on the report and which were not recorded on the last inspection report 5 years ago by a different inspector/company. Either his report has failed to record the bad circuits that do exist, or he is recommending to replace circuits that the EICR does not indicate need replacing/upgrading.  On many of the circuits on the EICR, the 'Maximum measured Zs' for an individual circuit bears no resemblance at all to the 'Zs at this board' + the measured R2 for the circuit.