First party games are a good thing. They provide differentiation between increasingly homogeneous platforms and allow the console manufacturers to deliver experiences tailor made for their machines.
Third party exclusives are a slightly different can of worms, but in my case I'm specifically talking about first-party titles, which at this point in time are literally the only reason one would buy ANY particular console. If the content isn't there, why bother?
I'd agree that first party games allow the developers to focus on delivering a quality experience since there are fewer platforms to develop for and thus creates greater focus for the team; however, in this situation, it's a port being developed by a separate studio after the game comes out on PS4 first (releasing at least 6 months later), which shouldn't affect the quality of the PS4 version at all.
Exclusives are definitely a primary reason to buy a console at this point so late in the cycle (especially for people that already own the other platform), but it's not the only factor. Cost and social influence (which one do my friends have?) play significant roles as well.
I'm just not seeing how this is a negative decision for anyone except maybe Sony. People on PS4 get it first with no reduction in quality and people with PCs eventually get a potentially worse or better version of the game depending on port quality.
As someone who owns a PS4 Pro but was hoping it would come to PC so I could play it in 3440x1440 (hopefully), I'm super excited for this news!