Mao,
If you're asking me, my response:
Not sure, but assume I know the old flies you're referring to.....those tied with 2 large feathers?
I would say this:
1. I have never, personally tied, nor fished one.
2. I would need to put one in a slant tank to see what such a fly would look like from beneath the water as it floated, hopefully, head-first toward the sunken trout. Trout spend little time 3.5 to 4 feet above the surface looking at the artificial or natural as we do while wading in the stream.
Perhaps, from a couple feet below the surface, and coming at the trout, these wing tips look like divided wing tips.
I couldn't say, for sure, without putting one in my slant tank and observing it.