Yep, reversing penalties is a rugby thing, albiet quite a good rugby thing I wouldn't mind seeing in football!
The overarching principal in football is that once play is stopped, the restart is then locked in stone. The only exception to this is if the referee realises the original reason for stopping play was incorrect (with or without the help of VAR), in which case they can then apply what would have been the correct restart in the first place. But even that is totally unaffected by any offences that occur after the whistle. EDIT: OK, not the "only" exception.