It's such a weird decision.
It almost makes me think there must be some weird technical or platform holder policy regarding DLC across gens that's tripping them up.
When I try to work through the logic I just end up confusing myself.
Here's my nonsense thought process, I wrote while very tired:
505 - Every PS5 version of Control Ultimate Edition includes the DLC, so we can't give the upgrade to PS4 owner who might not own the DLC.
Solution: Make a version of Control for PS5 that doesn't include the DLC.
505 - That requires more testing of the next gen versions as we have to test with and without each DLC pack to match the PS4 version. That's too expensive so we wont do it.
Solution: How about including the free upgrade as part of the season pass? We've seen other devs add more content to existing season pass owners in the past. This means you know everyone who is playing on PS5 is entitled to the DLC.
505 - That's a good idea and it's what we should do. However, this leaves out players who bought the DLC individually instead of buying the season pass.
Solution: That's got to be a tiny percentage of people who bought the DLC, better to disappoint them than to anger your early adopters and season pass loyal customers, right?
505 - No, we'd rather put all the current owners in the same boat. Cleaner this way. Existing fans will pay again to get the next gen improvements, or they'll happily play the PS4 version PS5 via backwards compatibility where it'll run at a stable framerate with quick loading. We're doing people who buy the Ultimate Edition a favour by giving them the next gen upgrade for free.
I can't make it work without coming to the conclusion that greed is at the heart of this.
Which it always is. But I love Control and Remedy, I want to find a reason that doesn't boil down the greed of their publisher being willing to anger their fans.