PS5 not really my thing, so hopefully someone else will chime in but you might be able to help them out by measuring the resistance to ground on the 12V rail and providing the reading, while it might not be a dead short, you might be in a situation where you have a soft short - which i think you do given the fuse blew (it wouldn’t blow for no reason). If it is a soft short, then your not going to have much luck finding it with a bench supply and detection with heat, so you might wanna play the o’l hot cold game with your meter in resistance (provided it has the resolution) to narrow down the culprit, just to save you pulling things off one by one.
For more details about this, check this thread for a similar situation on a Switch, same principle
Other thing to watch out for is, you could have a short on a sub rail, so it’s worth checking any sub rails too prior, as a short downstream could pull your 12V rail low as a result.