I do not know what level you are playing, and what site, but my my case, at micro, low level the 21-15-10 does not fit, work. Or at least follow that I am less profitable.
But I play 30+% of turbo, hyper tourneys, where I have 35+% ITM, if I am in the money, it goes really wild, mostly depends on the other players, some follow the same like me, so even under 5BB I play quiet tight against them, but there are the other 2 main type, the calling stations, and those who do not recognize it is turbo or hyper, so they still wait for monsters until their stack burns by blind raise, the favorite oppononents, they usually have pretty good stats anyway.
Generally under 5 BB every suited connector from 76 is allin for me from any position. from mid, late positions, I can't even make a rule, sometimes, even the worst cards good for a steal against the monster catchers, as they can fold BB even from 2BB without reason, no pay raise, bubble.
Even I do not get totally correct the turbos, especially hypers, but there are plenty guys, whose totally out of any logic, knowledge what they play, they just register for fun and for the fast game, I guess.
I have tried the hyper 1 table SNGs, and watched the regulars there, I recommend you try that, you can pick up something, how the profitable hyper regs play there, as almost all the time with 4-5 players the average stack size goes down under 5BB
Yesterday, I got call from them from BB with cards like 76o, 24s and they were about relegate exactly before money, they had room to fold.... so really hard to set a range, how to play it under 5BB
Oh, I forget the other favorite ones, the limping maniacs, whose are able to limp with everything from early position, too, and getting just a mini-raise, they fold... from 4-5 BB... hard to make sense in hyper tourneys, the turbo, with 5 min blinds is different, highly different.