They are connected but in practice there is definitely a big separation between lemmy and mastodon.. you see mastodon posts on mastodon, lemmy posts on lemmy. yes its possible to view lemmy posts on mastodon but its fucking garbage integration, i have never seen a lemmy posts boosted on mastodon it just doesn't happen.. if I see a mastodon post here its in the form of a screen shot.. the communities are effectively separate