The problem with this is that that following is only worth something if they actually see your posts, and stats on twitter makes it clear how small a proportion of your following will see any given of your tweets. Other interaction drives that home as well. Typically people seem to largely get far more engagement with a far smaller number of followers on Mastodon, and the same will be true on other new platforms for two simple reasons: Attrition and the algorithmic feed. Most long lived accounts will have a huge number of followers that have simply stopped using twitter, and secondly the default being the "for you" tab means that people have a habit of following accounts they never engage with or ever even see a tweet from, and so the follower numbers on Twitter are vastly overestimating how many people are actually meaningfully "following" you in the sense that they're still logging in and seeing what you tweet.
Doesn't mean you won't still have a challenge building up a presence again on a new platform, but getting to the point of equal engagement in a new platform where users are motivated and active only takes a tiny proportion of your followers to make the move.
I addressed that in the sentences immediately following what you quoted, but to clarify the point on algorithmic feeds:
I think it is relevant to any new social media, because even with an algorithmic feed, unless it's really badly done, you'll first start to swamp out an increasing number of those you follow once you follow a large number and/or have given a strong signal about which of them you actually engage with, so you're likely to get a "honeymoon period" even with one where the need for a huge following seems less important because your followers are in that situation too.
Doesn't mean you won't still have a challenge building up a presence again on a new platform, but getting to the point of equal engagement in a new platform where users are motivated and active only takes a tiny proportion of your followers to make the move.