Well, they shown many multiplatform games in the conference that will be released day one on PS5 (or even PS4) too, but I assume it was better for them to avoid these two because some fanboys would be mad to remember they will have to wait to see them on their console.
So I think it was smart to don't show them. At the end, everyone knows they are coming and already shown them several times so didn't have to show them again here.
To do the same with every other studio they have at the same time would upset their fans. But if they first to it with Minecraft DLCs, then Minecraft Dungeons, then Ori, then Bethesda DLCs, then new games from the already existing and Bethesda/Zenimax IPs, some small game from Double Fine, some non-MS IP like Indiana Jones, after that some new IP or maybe an old known IP... their fans would slowly step by step accept them going full 3rd party in the same way they accepted to have zero exclusives and to see all their games being released day one on PC.
In the same way, Starfield can be a timed console exclusive and they can market it as "exclusive" until a year after release, once they announce and release it for PS5 and if someone complains they can say it was something they already had signed with Sony before the acquisition.
Not sure if ES6 is going to be made by the same team than Starfield, but if it's the case, assuming Starfield doesn't get delayed and gets released late 2022, then I think we can wait ES6 to be released as next gen launch game (if MS releases another console).