No disagreement here but an observation.

I have only come across one reference to a time imitation of the wing has made any significant difference to the effectiveness of a fly. It was in an article by Dr Malcolm Greenhalgh in Fly Fishing and Fly Tying. He was fishing the river Lune in Lancashire late in the evening, with strong low sunlight. Patterns with wings were taken, those without were ignored (given all other considerations were the same). Malcolm believed that part of the "key" the trout had locked on to was the shadow of the wing on the natural.

Ever since I started tying I have been told that the wing is more for the benefit of the angler, making the fly easier to see, than the fish. Malcolm's experience seems to bear this out.

Cheers,
A.