Huh, I've raced for 10 years and never used tranny fluid in ANY of my bikes. I had a banshee for about 6 years and always used 10-30 in the clutch. I started racing bikes on a 92 YZ250 then a 93 CR250, a 96' YZ250, a 99' YZF400 and I ended my racing days on a 00' YZF426 and never used tranny fluid. Maybe we aren't on the same page here but banshee's don't need tranny fluid for the clutch.
Motor oil, car tranny fluid, or "motorcycle transmission fluid" can be used safely in 2 strokes. All the bikes you had listed were except the YZF426. That NEEDED motor oil. No options there. Just owners preference with 2 strokes. Your manuals told you motor oil... for you banshee, for your YZ, for your CR, etc.
Lube is lube in a 2 stroke. It lubes the clutch and the tranny at the same time, as well as all of the shifting components.
If you plan to use tranny fluid, it must be wet clutch approved. ATF Type F is wet clutch approved. Just like motor oils for motorcycles must be wet clutch approved.
Talk with engine builders... the best engine builders in the country and ask them what they run in their bikes. Whether it's on the track, in the sand dunes, or in my case, on the hills and drag strip.
ATF Type F tranny Fluid. Why? It's light, wet clutch approved, shifts like butter, and will not hurt a thing. Sometimes temperature will make heavier oils thicker or lighter than preferred, and this will make shifting gummy. Which can make or break your times or will be the difference in coming in 1st or 2nd place.
However, it breaks down faster than motor oil or thicker motorcycle transmission fluids. Thus, it needs changed often. I changed it after every ride. It was cheap enough to do so. But worked like a charm.
There are articles on this online... you can certainly read up on it. Or, if you'd like, I will post links to make it easier.
Pistons are lubed by the oil you put in your gas. I am sure you knew this.
Here is Bel Ray Gear Saver... a "transmission fluid" used in 2 strokes. I have used it, and will most likely use it this year with my new clutch plates and fibers I put in. I was running the same clutch fibers and plates for 6 years until this year. Took the clutch out, looked at them, and they still had life in them. With the power my bike puts down on the ground, and don't forget, it's no everyday banshee, you would think I would have fried a clutch or 2.
I don't want to start a peeing match, and certainly don't want to stray off topic. But a Clymer's Manual (not your owners manual) will explain alot of this. Motor oil simply wears down quicker and is heavier/lighter than some of the tranny fluids out there made for motorcycles.
Banshees can safely run ATF Type F tranny fluid... I repeat, ATF Type F. It is for Fords I believe, but ATF is wet clutch approved. And is tranny fluid (2 strokes have 1)
It's cheap, and effective.
Banshees do need tranny fluid, or motor oil if that's what you prefer and would like to use because that's what the manual says... However, if we all listened to the manual that comes under the seat of a bike rolling off the showroom floor, we wouldn't have aftermarket parts on them either.
That's the best I can explain it... if it's still not making sense, then I don't know what to tell you.