Hey dude,
i just saw your question and the answers so i had to register real quick and give you my opinion on it because i am a DoN player myself and i think it is def. not a fold and here is why:
let's imagine we are the player "backtoggrind" :
Big Blind is knocking at our door and the chipleader is sitting to our right, which is bad, because u rather want the chipleader to your left, so you can jam on him with many hands to collect blinds. (at least when you are in the danger zone). A skilled chipleader (with a small/decent chiplead) will almost never call because he rather wants the small stacks to bust each other ofc. So, having the chipleader to your right is shit and backtoggrind knows this.
He shoves from UTG and he knows this very well too. He knows that his shove looks ultimatively hyper strong in this situation. If he'd hold a monster like JJ+ he would rather not shove. He'd minraise or put some donkraise like 3.5BB because there is the possibility that one of you guys loses patience and rejams with ATs+ or even worse. i've seen him doing these monster-minraises in similar spots, it's part of his play. he might mix up his play in these situations but he def. does that.
He might shove monsters during the first games with new/unknown players in the hope that someone looks him up and has a trauma/shock from this point so they will never look him up again if he shoves from UTG because they remember what happened last time.
So if backtoggrind folds there UTG, "NewLife67" or YOU would shove pretty often and that means that backtoggrind will be the shorty in the next hand. Due to this, his fold equity will drop down heavily. He simply does not want this to happen. If he folds he will be forced to shove toooo many hands in the next rounds only to stay alive.
If everyone folds and the chipleader collects the blinds, the chipleader will have a massive chiplead on backtoggrind which is bad, because then he can easily force backtoggrind into an all in next round without even risking his own life.
So, what i wanna say is: if he folds, no matter what happens between the 3 other players, it has always a bad outcome for backtoggrind.
i have played some DoN's with backtoggrind and i remember him jamming A7o UTG in a veeery similar spot. That was the only time i looked him up in a spot like this but i would bet my ass that he jams any A, even more K and suited connectors, he might even jam any two cards because folding is crap in this spot. Guess it depends who is sitting at the table with him.
It's a very special spot and my thoughts only go so deep because backtoggrind is an experienced player and i expect a sneaky preventative shove like this from him, only to not fall back on rank 4.
So, yeah... Ofc you run into monsters occasionally but i'd say that you have to call because a player like backtoggrind shoves too much bullshit there.
CALL CALL CALL!!!!