Holding is part of the syllabus. It does not form part of the test. However, if ATC direct that a hold is required, the applicant must be able to enter the hold and fly the hold correctly. However, back in 'self-improver' days, many an IMC rated FI without an IR seemed to want to see the student practise endless holds - more for their own benefit than that of the student, I would guess. Same went for those gits who would fly 'demo ILS' approaches with ab-initio PPL students and then log them as part of what was then the mandatory 4 hours of IF training.....
The IMC Rating is a most useful rating for anyone. Personally I still think that FI(R)s should not be permitted to 'upgrade' to FI until they hold an IMC rating themselves and have demonstrated the ability to teach applied IF.
There have even been cases of FIs who, not only still had the 'No applied IF' restriction, but also didn't even hold an IMC rating themselves applying to become FEs.......