From what I've seen from experimenting, the only accounts that seem to have weight on each other on lemmy are my lemmy and kbin accounts.
But I suspect people doing this are more about getting exposure for a point of view or link.
If you post on lemmy and boost on kbin your followers on mastadon I think can see it as a post. So it pushes it all around without a repost and links back to the original.
I think it is pretty good that this stuff works together mostly seamlessly.