Ok, Petrification is permanent, im aware of that, its that way in every edition of DnD. It isnt in OS, probably because in OS you dont get to fight an actual medusa, but just use a spell that simulates that effect and thus it only lasts for its duration. But realy, thats the difference between a video game and a DnD campaign.
permanent petrification is only interresting if you then have a DM that deals with the consequences of it. Such as offering an actual solution. Otherwise its just "load your last save".