I think it's just a comparison because during the Reddit Exodus people often suggested Discuit instead of Lemmy because ActivityPub is "too complicated". So I guess this is a good demonstration that federation really is our best hope at replacing the big billionaire social media platforms.
As another point of reference vs Discuit's 6,787 registered users, Lemmy has 1,904,195 registered users. Kbin has 66,175, and Mbin has 5,453 registered users.