I saw this earlier. My guess is that it was a margin call.

edit: and with the new link you sent, it says the customer probably didn't have collateral. They will absolutely sell on a margin call.

It's not an option. It's common stock and a long position.

A margin call you can settle with cash. There's nothing here that says "you didn't deposit cash so we're selling your position(s) of value to make margin"

I mean it's possible, but I'm in no way going to default to that explanation absent evidence.

Edit: it explicitly cites the "risk of brokering your position" in GME shares. If this isn't faked it's an astoundingly, jaw droppingly, nakedly and utterly amazing thing to do.