Hi everyone. I have mostly played 0.05$ NL, but recently i decided to move to 0.25$ NL. Bad choice because my bankroll was too low for it but thats a different story.
Anyway, i was playing 20-50 BB tables and first thing that started to annoy me were certain shortstacked players that have been doing lots of preflop all-ins.

Now, I am familliar with shortstackers strategies, they play top hands only, and usually raise or allin preflop, or shove it on flop after they preflop raised.

But i think these are something different. They always play shortstacked, with 5$, if they fall below they rebuy to 5. No matter whats happening on the table they will go allin with AA-TT, AK, AQ, possibly AJ (not sure), and probably all or some, mid and low pocket pairs.
If they lose they rebuy, if they double up they leave the table.
And thats it, thats all of their gameplay, well, rarely in a few of those suspects i have seen normal preflop raise, and very aggressive postflop game if they hit something (same range AA-TT, AK, AQ, etc...).
Strategy seems solid, they lose some, win some, and quite often win other players preflop raises. Also, it is enough to minraise them if they are in BB position, to steal their blinds if they dont have top hand.

Anyway, my question is, is this some kinda grinding strategy, or should i suspect im playing against bots?