They both federate and they both look the same I think.

However, Mastodon search works by tags iirc. And kbin/lemmy users tend to not use tags. So discoverability is low.
The Microblog section is supposed to add the magazine’s tags to your posts there, though I don’t know if it currently does. I remember reading issues about it not being the case, but those were rather old, so not sure about the current status.