Yeah the reality was probably that someone thought it would be a good way to boost some numbers somewhere to justify their position or get a bonus for 'increasing the user count' or other nonsense.
I have a theory it's part of the same effort that's resulting in some Sony-published games getting PlayStation trophy support on PC. They probably want to eventually accomplish something similar to what Microsoft did with cross-platform services between the Microsoft store and Xbox.
In similar spirit, my theory is that this is part of how they fix the issue where PC players and PS5 players have issues making/accepting friend requests. Recently the players ID's were changed from being randomly generated to a set assigned ID, and I would have bet money that the PSN account linking could have been a way to resolve whatever issue was going on there.