How long does it take to make a proper PC port? I don't think Sony wants to start making multiplats and rather stick to ports as they have always done. (Concentrate on the best optimized version for ps5 first) So the turnaround time from PS5 release to PC port is how ever long it takes to make a proper stable port after the PS5 release had its day one patches.
Better to release a working version on ps5 first, then a working version on PC, instead of a work in progress on both at the same time. Or worse, develop on PC first then find out there are lots of bottlenecks on console like with CP2077.
Can't you buy PC versions from Sony directly atm? They have the psn store online, but I see there is indeed no PC segment under games, and no PC version for horizon zero dawn. Kinda odd, but you don't need a PS account for the Steam version I assume? I guess Sony really wants to keep it separate?
Considering they created the PS PC label, I would say it is very likely for them to start to offer their PC Ports on the PS APP and online store. Could even end up with cross-buy options.
Microsoft does that and it's definitely an advantage to buy from them instead of Steam when you own an Xbox along with your PC (Xbox APP). Buy once and you get the PC (Xbox APP) and Xbox versions. You also get cross-save and shared achievements (if you care for those). Most PC gamers don't use the Microsoft Store even with this, and even before their games went to Steam. So even if Sony brought their games exclusively to their own PC Launcher and has cross-buy, I don't think they'll sell well. So it's best to offer their games on Steam (and GOG) along with their own storefront.