These are interesting numbers for engagement but don't mean as much without equivalent stats for the other platforms. It's a little like when a news story quotes only a percentage (but not the absolute figure in $) or vice versa.

Agreed.

Assuming they use the same principles everywhere, they're getting more views on Mastodon and Bluesky? That is surprising.

Not really, their target audience is much more likely to hang out on Mastodon and Bluesky. So even if the impressions might be fewer the quality of them is almost certainly higher.

Also if you tweet a link to the content instead of tweeting the actual content, you get penalized by the algorithm.

They do this in almost every tweet.