I think it just seems disingenuous. Microsoft "federating" AI generated articles and fragmenting the comments leading to ActivityPub looking like a mess when in reality Lemmy and Mastodon and other services do interoperate in ways that are expected.
Maybe a better question for federation would be "can users interact with eachother?"
You can't follow Lemmy users on Lemmy either. I actually think the Lemmy developers are planning on improving how Lemmy federates with other services, but they just have other stuff to focus on and aren't as well funded as Mastodon.
However, you can follow Lemmy users on Mastodon. It's also possible to follow Mastodon groups on Lemmy
Look at where my account is from in this comment
This account is actually a Mastodon account I created a few months ago to test posting and commenting on Lemmy instances. The comment, and this post did show up on the social.rust-lang.org instance, so I think they're also able to just reply to posts where they're pinged.
The following image shows it on their Mastodon instance.
I think I'm just kind of being somewhat extreme about it too. I mean, like, Microsoft has had support forums in the past. (I think even some that have been removed, etc) Lots of stuff like this moved to reddit, but I could see it possibly being successful with federation today.
(There were reasons it failed, like, bad UI, miserable account control, differences in how answers were displayed, etc)