Mastodon is an order of magnitude (or two) larger than m.b. currently, so I'm not too surprised. One also needs to be on the lookout for such tools and then to be willing to try them. I suspect given the thrust of his post that he's taking the preference for the broader independence of the web and may prefer the content he's actively chosen to subscribe to in his feed reader. Given his technical ability, I suspect that micro.blog would only be yet another feed reader he'd need to check for updates.