no you cant steal cash thats deposited into the bank account
as far as i know, everytime you earn money in gta online you have to take it to an ATM or youll run into risk of getting robbed by other players.
that description explicitly states that the money gets deposited on your bank account
My guess is this goes to the ATM card and can't be stolen. Cash picked up in game can be stolen.
There is no way Rockstar is dumb enough to let someone spend 20 bucks of real money and lose it in half a second. The backlash isn't worth it to them (it would also result in people spending less real money buying virtual currency).
This is a mainstream game, not EVE.