Pilot DAR:
I certainly agree that there could be aircraft types (sailplanes) for which the "don't fiddle the flaps" theory might not be as appropriate. As I have very little experience in sailplanes, perhaps that is beneficial for them.
It was the Cessna/Piper XXX types which were the subject of my opinion. I'll be doing some flight testing on a single with 60 degrees of flaps available, so I'll do some experimenting in the weeks to come, to gather more objective data.
I doubt we're actually in disagreement. Don't fiddle with flaps on the approach unless you know what you're doing must be the right approach.
It would interest Cessna/Piper XXX drivers to know whether raising flaps might help them, but even then it should be a case of "don't touch" until they've practiced it safely at height.