RS,
The AAIB invites the CAA to write a piece of advice so that FIs know what the CAA considers to be best practice.
They very much balance their view by stating:
The risk of a genuine failure resulting in an accident must, however, be balanced against the risk of one of the necessarily much greater number of practised failures going seriously wrong.
Not sure whether your interpretation of their advice indicates that AAIB think the rules should be changed.
I read it to mean that they would like a clarification on what the CAA thinks would be the best way to train folks for FLs and EFATOs.
Would be good to read BEagles comments.
FD