It was revealed years ago. MS has an Indie clause where Indies cannot release on PS before Xbox, they have to release simultaneously. If they do release first, then extra special (exclusive content) has to be in the Xbox version when it releases.
For small Indie studios who don't have the financial backing or manpower, it was crippling to them... so some had to choose to publish on only one or the other since they did not have the means to do both at the same time, or alter their game for extra content.
It became a gamble for a lot of them.
Yeah, I am going off of today (the last 2 decades) when licensing restrictions shifted big time. Hence why a lot of sports franchises went belly up, etc.. I seen some of the things SSD had to go through with MLB The Show back in 2010-2013, and it was a nightmare on the licensing side of things. Lots of red tape and back and forth with the MLB their partners, lawyers, etc..
It's a little smoother now that there are licensing and ad packages more available, but also more expensive than in the past as well.