Disagree.

In the table the typical context that the word "should" should be in is in an informative element.

If the word "should" was used in a normative element, then you should do it.

In the case of 421.1.7 the word "recommended" is used in the normative element of the regulation, it is not within an informative element (the notes). So to substitute it with the word "should" would be out of context. If JPEL 64 wanted to use the word "should" in a normative element, they would have done so, and AFDDs would have to be fitted, just as if they used the word "shall". They used "recommended" because they only, simply recommend that they be fitted.

It does seem a bit convoluted though

Edit; The table is based on this document Microsoft Word - Rules for structure and drafting of UK standards 170420 FOR PUBLICATION (bsigroup.com) Which states "The auxiliary verb “should” is used to express recommendations. In a specification or test method, the auxiliary verb “should” is used only in informative text (i.e. notes, commentary or informative annexes). In a specification, recommendations may be used to indicate that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others, or that a certain course of action is preferred but not necessarily required, or that (in the negative form) a certain possibility or course of action is deprecated but not prohibited." and has been re-worded a bit in BS7671.

Disagree.

In the table the typical context that the word "should" should be in is in an informative element.

If the word "should" was used in a normative element, then you should do it.

In the case of 421.1.7 the word "recommended" is used in the normative element of the regulation, it is not within an informative element (the notes). So to substitute it with the word "should" would be out of context. If JPEL 64 wanted to use the word "should" in a normative element, they would have done so, and AFDDs would have to be fitted, just as if they used the word "shall". They used "recommended" because they only, simply recommend that they be fitted.

It does seem a bit convoluted though

Edit; The table is based on this document Microsoft Word - Rules for structure and drafting of UK standards 170420 FOR PUBLICATION (bsigroup.com) Which states "The auxiliary verb “should” is used to express recommendations. In a specification or test method, the auxiliary verb “should” is used only in informative text (i.e. notes, commentary or informative annexes). In a specification, recommendations may be used to indicate that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others, or that a certain course of action is preferred but not necessarily required, or that (in the negative form) a certain possibility or course of action is deprecated but not prohibited." and has been re-worded a bit in BS7671.