Well, that's a self evident falsehood on the part of Microsoft. PS4 was playing Rocket league with PC players long before Microsoft thought up their latest smoke and mirrors scheme to try to make themselves look like some kind of savior or champion of gamers interests...
Let's look at the evidence shall we?
PS2 could play FFXI (and a couple of other games IIRC) cross platform - even with Xbox players in the days before Microsoft cut access for Xbox outside of XBL that is. The 'champion' of open, cross platform play imposed a restriction on their own customers designed to milk tem for more money. Sony was good with cross platform play in the PS2 days - during the infancy of online gaming.
PS3 could play FFXIV (I believe that were a small number of other games with cross platform ability too) with PC and MAC players - seems like cross platform play was A-OK for Sony then. Could Xbox One? Nope.
PS4 can play many games with PC and MAC players, FFXIV, Rocket league ad others I am certain. Could Xbox One? Nope until MS apparently saw the light...
Except Microsoft embraced openness and cross platform play in such a way that it would require Sony to open PSN to external networks. Given that PSN itself was completely breached - rather famously - a few years back, and the more recent hacking of Sony Pictures, Sony is understandably reluctant to open their network to anything. However, when asked about it, Sony points out that they already support cross platform play with multiple platforms and point out that developers are more than welcome to do it if they wish.
So, if MS is so interested in cross platform play with PS4, why do they impose requirements to interconnect Xbox Live with PSN to make it happen, when clearly that is not required? Couldn't Microsoft have similarly said that developers were welcome to implement cross platform play if hey want? Although had they done that it would mean that Xbox would be able to play online without Xbox Live, which Microsoft will not allow, after all, it would mean Xbox players online in MMO games without paying anything to Microsoft, and that we just cannot allow...
Basically, this is more of the same Embrace, extend, extinguish strategy that Microsoft is well known for in the business world.
They 'Embrace' openness very publicly, saying they see the light and Xbox players should be able to play with everyone...
They extend that cross platform play 'offer' but include a poison pill that they know Sony cannot accept = open PSN to XBL, or no dice.
The extinguish phase comes when people who don't look past the headlines take it at face value that Sony is obstructing something that they have in fact supported since PS2.
Don't fall for the Microsoft lie. If Microsoft wanted Xbox players in Eorzea, they could have been here since day one of ARR. All MS needed to do was allow Xbox players to access game service providers outside of Xbox Live without mandating XBL Gold membership. There is no technical need for integration with PSN to make that happen, quite the opposite. In fact, it requires no real software implementation at all, other than REMOVING an artificial RESTRICTION that Microsoft themselves put in place. Far from looking out for gamer's interests, Microsoft actively works against gamer's interests by finding ways to charge more for less.