Going one notch back, to Acc or even Off, won't lock the wheel. You will lose power steering assist, but as a regular driver of a vehicle with manual steering, that's not really an issue at anything other than a complete stop. Power brakes going out due to loss of engine vacuum is more unsettling and not as easily compensated for if you don't know what happens, but there is also a reserve of vacuum in the booster for 1-2 stops with some assist, you don't instantly get a hard pedal and reduced braking.
As mentioned above, it's not about the key turning off being bad as much as it is them knowing there was a problem with a fairly small part and just flat out refusing to address it. That's bad news, and them getting caught now is not good at all.
I'll still keep my cobalt, i'm not worried lol.