So I talked to blizzard support they told me to go to the forums and here is just what I said copy/paste:
This isn’t really a problem more a suggestion but I think that you guys should make it free if you own overwatch on ps4/xbox that we should be able to play it free on pc this would be very nice because it does say on the website I own the game on ps4 but I thought maybe that would let me play free but I was wrong this seems like something that should happen please talk to someone about it at blizzard to consider this thanks for reading this.
Console versions are technically licensed to each platform, (meaning Sony and Microsoft each take a percentage from each license sold for that Platform) and really this licensing is about those console platforms wanting you to stay on that platform and not switch to another. This is why there is no cross-licensing, cross-account, or cross-play features across platforms in most games. Granted games like “Fortnite” are tearing down some of those barriers, but for now, things still comes down on each platform wanting to make money on that platform.