When you go to a race where kit is not necessarily mandatory in all conditions (i.e AS, BM, etc)

But you see a sign, or are told "FRA kit regulations"

The decision has (as stated in the rules) still been made by the race organiser... It's just basically a simple and interchangeable way of letting you know what they require you to carry. The premise being that everybody should be well aware what FRA kit is.

I don't think it means that the written rules have changed and you therefore have to carry full kit at every AS, BM, race...