Yeah, you've made a point I forgot to mention: where you tie in the wings depends on how you make them. If I were going use Catskill wood duck wings, or quill slip wings and really wanted to closely imitate the actual insect, the half way point wouldn't be absurdly far back. OTOH, if they were made with a hackle burner, they could be much further forward.

To answer your other question
Do you think any tier adjusts wing tie - down point from insect to insect.?
The photos I see, by the same tier, appear to have the same wing position regardless of the insect bring imitated?
No, I don't anyone varies the position of the wing from insect to insect. They pick a point that works for them and stick with it. (And I think that the "mechanical" aspect wins out over the "imitative" aspect every time.

The original Adams was tied with the wings right at the eye of the hook. I can't think of any insect that has wings on it's head, but yet the Adams obviously caught fish right from the start.