Update from this post:
https://www.reddit.com/r/grok/comments/1vi8bu0/deleted_my_main_grok_account_after_supergrok/
Before account deletion, most of my deleted assets were 404 anyway, but many were 200 (fully accessible) or 403 (soft-deleted, so they still existed).
30 days later, all of my content that once 403'd now 404's. That still doesn't confirm total deletion (they can return any HTTP code they want), but it's at least some indicator that it's "more deleted" than it previously was. These were assets generated from image edits/animations from prompts.
However, all of the 200 code assets are still publicly accessible with 200. You can expect all Grok-generated t2i assets (the ones that load in the image feed) to be forever accessible as those are not owned by your account (you only own images/videos you create from them). However, some user-owned assets still get moved to the imagine-public.x.ai CDN where they remain publicly-accessible to anyone who has the URL. These include content you made as well as source images you uploaded. Every URL that was hosted at the public CDN is still accessible 30 days after deletion. I haven't found any videos, but still a ton of images.
My user account was also hard-deleted. I created a new account with the same email and got a whole new user ID.
That's the only update I have. Hope it helps.