Fully understand Sony not wanting crossplay and (kinda) support it.
For example I bought Dark Souls Remastered on PS4 specifically to avoid PC hackers.
And what happened, PC version rife with hacking, PS4 version free from hacking.
In DS:R you'd even have folk hacking items, giving them to other players, and getting the victim softbanned since it was in their inventory. (
https://www.pcgamesn.com/dark-souls-remastered/dark-souls-remastered-softban)
Sony has a walled garden, there are pros and cons to that. Polluting that with PC players isn't necessarily a win.
For example if PC hacking affected the PS4 version I would have bought DS:R on my 1080ti PC instead, Sony would have lost a sale. And this walled garden essentially mean't I had a way to avoid hackers messing up my online which otherwise would not have been the case.