It does get translated but it takes some weeks for them to do it. It would be nice if they did it, but meanwhile, I'd suggest just listening to the unofficial one (hardly anyone seems to listen to this and seem unaware it exists): https://www.youtube.com/@ilunari/streams
They do summarize the points. It's all translated on the forums and summarized in the Live Letter forum. You can go back and read their summaries of all the past live letters. But content creators do that as well, and much faster.
The live stream I would guess is to authentically talk to everyone and create hype. A lot of people tune in, excited to watch the trailer the moment it drops, and discuss the news together. Not that he does it a lot because he's probably not very good at it, but he has read stream chat on occasion, and particularly tried that a lot more during lockdowns to try and make up for the lack of connection.
Meant as a goal for someone to reach, even if they never attain it. Seeing a shiny weapon and thinking "I'll get that someday" has always been a healthy thing in an MMORPG because it's one of the goals they can set for themselves when they are new.
It's also deliberately designed as stream content. It's meant to look good on twitch streams, and that's on purpose, because they don't expect many people to actually do it - although I think in practice, way more people clear ultimate than they expected when they began making it.
When I was on Crystal, I never saw a single Ultimate weapon except in a dungeon once (it was a Dragoon). Then I transferred to Aether and everyone had one. Almost everyone I knew or had a passing interaction with had one. The contrast in Limsa between Crystal and Aether before we had DC travel was massive. It shows that given a better environment ie. PUG ultimate culture on Aether, that it can transform how many people do even that content.
I agree that there is preparation involved for raiding like this and Yoshi-P is actually aware people take time off work for release dates so he doesn't change release dates lightly.
However, Yoshi-P has actually said multiple times that he can't guarantee Ultimates on a consistent schedule like everything else because of the sheer difficulty of producing (nevermind testing) content like that, so although we normally get them in .11 and .31, it would be wise to not take that for granted as we've had exceptions to the .31 in particular.
If the static can't stick around that long, it may be a better option to form statics when the release date is actually known, even if it would impact any sort of intention to world race.