I feel like the reason Sony has decided to do this is to stop players who were previously banned from the game for whatever reason on one platform from re-joining the game on the other. Given the game is cross platform, I can actually understand this at least to some extent. So whilst I think there was no ill intent, Sony have clearly not thought this through. The fact this might effectively bar people from playing the game because PSN is not available in all countries whare Steam is available a huge oversight. If this was always the plan, they should have shown people the big, flashing sign with the siren saying "You WILL eventually need to link a PSN account to your Steam account to keep playing" before people bought the game. That's the part that really bothers me.