Perhaps it should be one of currency on type, rather than a straight out TT?
This would be particularly relevant for tailwheel, and maybe also twin,aeros and formation work. Given that the endorsement or conversion training is usually given in the LH or command seat, it's a bit optimistic to then allow the recently endorsed FI to switch seats, and demo from the RHS.
In Oz, there's not even a requirement for an endorsee to fly the aircraft solo to qualify for the tailwheel type. Without some 'command' time, how on earth can the recent endorsee be capable of instructing?
I agree with previous posters that at least a check ride for junior FI's would be prudent - given that our insurers are becoming ever more nervous.
happy days,