Not being up on current slang, I'm unsure what the turbo or sniper button could be, but I don't see how the forward assist could be either of those.
The first M16A1 I was issued had the "teardrop" forward assist button, and that was the friendliest feature I've ever experienced on a fire arm. I mean that sucker would reach out and hold on to EVERYTHING. Sticks, stems, leaves, even my web gear and clothes. And, don't even think about being able to move underneath a camo net!
100% of my use of the forward assist was getting it unhooked from what it got snagged on. And, I'm serious, 100%. I never used it as a forward assist.
My second M16A1 was newer and had the round button. Reduced the snag factor about 90% and got the same amount of use as a forward assist as the previous rifle did.
I did use the FA on a civilian gun, got a batch of poorly sized ammo, and used the forward assist to ensure complete chambering. One time, it did. The next 4 times, (because I was stupidly stubborn) it did not fully chamber the bad rounds, it jammed the gun up so tight you could not open it with the charging handle, and I had to disassemble the gun to clear it.
For comparison, I was also shooting a Mini 14 at the time, and the bad ammo only failed to chamber about 1/4 as often as the AR jammed and a rap on the back of the op rod handle always locked the gun shut, and it fired.
The Forward assist was a "solution" to the design having a charging handle that only worked in one direction. I've had HKs, FALs and many others, and for me having a large, STEEL charging handle that moves the bolt back when pulled back and moves it forward when pushed forward is the superior system.