I wouldn’t assume that crucifixion was always done exactly the same way. People can be nailed through the wrist, or they can be nailed through the palm and their weight supported a different way (ropes around the wrists, etc.).
It probably depended on who was doing the crucifixions.
The professional executioners probably did it through the wrist, but what if they had the day off? Joe Schmoe centurion probably had no clue how to do it properly and all bets were off.
True...one of the apostles (I think Peter?) was crucified upside-down, wasn't he?