brokerage firms have a first in first out sell protocol!
You set how your shares are traded, also, you can believe what you want, but firms loan out your shares no matter if it's a cash account or you have a sell order in, they just do.
Why, because they can, Gensler doesn't enforce the laws, plus if and it's a big if, they're caught, they get a pandy dandy fine, but they make a ton loaning out your shares.
Gensler wanted to change things, he'd get judges to send the thieves to prison with Bubba.