In order for the system to work, they would need to do this for all the PS3 games, otherwise we could just use the old keys that the old games use.
So new and old games alike would have this requirement to connect to Sony for BD key authorization. There is no other way to do this without applying the new key system to every single game the PS3 has. otherwise there would be gaps and vulnerability's within the new system.
This is why the hackers said this is the final blow to Sony and that they would need to release new hardware to fix this. Because Sony can't just up and create a new key system without forcing people to have a internet connection just to play games. And since the older PS3's and older games don't mention anything about being forced to have a net connection to play, Sony would get owned in court if they tried this.
As for the PC game you mentioned, that is slightly irrelevant. Each game on the PC is a separate entity in the universe of PC gaming. And it doesn't matter what PC is used to play them. With PS3 games, we are limited to only playing these games on the PS3. The PS3 is a propitiatory piece of hardware owned and controlled by a single company, the PC is not.
It's Ok for each individual PC game to have different rules and requirements. Because if somebody doesn't want to abide by those rules, then they don't have to buy the game. What Sony would be doing is forcing every single PS3 owner to follow these new rules for every game they play, even though they didn't agree to it or were warned about these rules when they bought their games or hardware.