You can find this at the bottom of the page on the Epic Games Store, where you can buy Beyond for PC right now.
Who owns what isn't the end of all discussions, there's contracts involved which might allow games to come to other platforms. Maybe Kojima really wanted a PC release and presented it as a condition for him to sign a deal with Sony, and Sony decided a Pc release later on was worth it for the sake of getting a Kojima console exclusive. As far as game devs go, Kojima is popular and famous enough that he probably wouldn't have struggled to find a partner if negotiations with Sony fell through
Ok you made me doubt so I had to go double check haha.
It is not quite as straightforward as I thought though I still stand by my coments.
Prior to the game getting its formal announcement at E3 2016, Kojima Productions announced they would be partnering up with Sony for their first game. At that point the deal was announced as a "console exclusive" (aka, timed exclusive that will eventually release on PC). There was even a Q&A from Sony (which has since been taken down) where they confirmed the game would get a PC release.
Since then they haven't brought up the whole exclusivity deal again. During E3 2016 Kojima just confirmed he was working with Sony with no mention of exclusivity, and during E3 2018 they just showed a trailer with no introduction or mention of exclusivity. The only instance I can find of them talking about exclusivity is for a vague "it's coming exclusively to Ps4 this November" statement.