nostr:npub1qg48cy9nkrm0pkeuz7e9zrzeq2n6lnlwyn30u9zd0xe07g9qvras00augv The full blog post does go on to say

we make no comment about whether Mastodon should be scalable. There are good reasons to limit the size of an individual Mastodon instance. It is our belief, however, that such decisions should be product decisions and not forced by technical limitations.

But yeah - the whole thing looks like just a product push for their development platform.