That's interesting but since the first reduction in diam/grains occurs after the line taper, I can't see why it would be better than a taper that graduates down from the line itself? Won't the additional back taper slow the energy wave down?
Two things I've done in SWFF situations (large flies):
a) cut the first foot of SW flyline off - it's level anyway. Not for trout lines but for SW and sinking tip construction using shooting heads
b) build the leader with more stout material and less reduction over the length of the leader.
Using clear intermediate allows shorter leaders, and sinking lines don't need a long leader most of the time anyway.
I have a hard time with long floating line leaders on Spey rods when the fly is too big or heavy. I don't throw any weighted flies for steelhead at all so I don't really have this problem, and with big flies for winter fishing the sinktip and shorter leader turns over big flies easily.
Sometimes I am not the most skilled at delicate trout presentations
maybe a little slowdown and speedup will help?
I am skeptical. The back taper on a FWF line is to reduce down to the running line so you can shoot the line, it doesn't help turn anything over. Just try casting 20 past the head on a Teeny, QD, Depthcharge or other radical back taper line and you'll see what I mean. For what it's worth, I would have to give it a high BS rating. I could be wrong, but it sure sounds wrong.