This will slow down development by being forced to implement interop where they shouldn't be forced to IMO, and will confuse less savvy users (e.g. "Why can't I send this $platform_native_content to Bob but can send perfectly to Alice in the same app?").
Controlling entities' presence within the public (the Internet) is one thing, forcing to do things within their own platform/domain is another.
Sadly, EU picked the latter.