Exactly; there's people on Youtube for example who've seriously argued that MS would be better off doing Day 1 releases for both Xbox and PlayStation, and that "simply" having the game in GamePass would be enough.
But, we already have enough data showing that having these type of ecosystem benefits in and of themselves don't sway things too much. How many 3P games have support for Smart Delivery and Quick Resume on Series, with no equivalent on PS5, yet sales ratios end up in favor of PS5? Quite a few, actually. The truth is people have their habits and you have to do something drastic in terms of the content itself to shake that up at a large scale.
And what's the one thing some people keep saying as a big factor for the success of platforms like PlayStation and Switch? Exclusives. So by that logic, why would Microsoft see a perfect opportunity to take a head-turning game like TES6, that could swing a lot of momentum to their brand and ecosystem, and handicap themselves by providing that content Day 1 on competitor platforms? Yes in the short term they'll get their sales, but they'll lose 30% of profits, lose out on Series sales and also lose out on GamePass subscriptions. Effectively, they damage their own brand long-term doing such a thing.
The truth is Microsoft are already providing a good deal of multi-platform content, from Minecraft to TES Online to Fallout '76 etc. No one is saying for Sony to bring SpiderMan or TLOU to Xbox, even though that's an audience of some 50-60 million they could be selling to (and just statistically speaking, if they sold 18 million copies of SpiderMan to an audience of 100 million PS4 owners, they'd statistically of sold an extra 6 million to XBO owners). No one is asking Nintendo to bring BOTW or Pokemon to PlayStation, Xbox or PC, even though they could sell dozens of millions of additional copies doing so.
So why are people saying Microsoft "must" bring the next Elder Scrolls, DOOM, Quake, Wolfenstein, Fallout etc. to PlayStation? Yes at one point those were multiplats but at one point Street Fighter was also a multi-plat until SFV. Wipeout at one point was a multiplat (due to prior contracts Psygnosis was still obligated to do ports to the Saturn and a later one to N64) until it wasn't. This is nothing new and eventually people got over it, they'll get over it again and just adjust to a reality where those Zenimax/Bethesda games are platform-exclusive to Xbox (in terms of gaming consoles; they'll naturally always be on PC as well).