So if it were clearly written on the Steam page, I don’t really get the complains.
It was optional for several months and the info on the PSN page contradicted that, so there was a lot of room for confusion.
Not surprisingly that PSN page was edited earlier today, but there's a million screenshots floating around already, plus you can check the previous version in the Wayback Machine.
And even if it was clearly written on all places, it's still a "too bad you didn't read the fine print, now you're past the limit time for a refund, so either let Sony track you or lose access to the game" situation which is very shitty. There's also the fact that they sold the game to people in countries where is PSN is not available, which should not have happened if that requirement was going to be enforced in the future.
Not hard to see why people would get pissed and lose trust in the developer. I also think that players have been annoyed for a while with this type of requirement (not specifically in this game), and they are now getting a good outlet with a lot of publicity around to vent about it.
The review chart is hilarious.
Doubt Sony or the developer expected this would happen.
Edit [May/04, 14h UTC]: Updated chart. More than 70k negative reviews already.