The example shown literally is a regular post simply marked “Sponsored” so it can be assumed that post would federate just like any other post. The only difference being the Sponsor marker likely being a Threads exclusive ActivityPub extension so unless other platforms implement that the post would show up as a regular post on e.g. Mastodon.
Them being in compliance with EU regulations while simultaneously blasting their ads into the Fediverse are not mutually exclusive. There are ways for them to do both. And to be fair here if the ads get federated they will likely be marked as such in some way so other Fediverse platforms should be able to filter the ads out easily.
The example shown literally is a regular post simply marked “Sponsored” so it can be assumed that post would federate just like any other post.
Instagram shows its users sponsored posts from accounts you don’t follow. Threads will do the same for users of its website and apps. These posts will not magically show up on Mastodon from accounts one doesn’t follow. If a Mastodon user would follow the profile of a brand, they’d get the posts from that account that would obviously contain promotion (just as any brand is free to join Mastodon right now and promote products there) but as @troed 100% correctly wrote: You don’t get posts from accounts you don’t follow.
Are you aware that a global feed exists on Mastodon?
No need for admins to defederate and take away the decision from grownups. Learn how Mastodon works instead of being hysteric because you believe unfounded conspiracy theories.