“Bluehost, for example, does the best job I’m aware of in keeping the largest number of WPs on the latest version”

What kind of a lame benchmark is that, for being listed on the page! So, because they host a large number of WP sites they deserve significantly preferential treatment to other hosts!? Bluehost is consistently one of the worst hosts around and recommending them to new WordPress users only does them a disservice. It’s no surprise that Bluehost is owned by EIG. Just ask anyone who’s been in the WP community for a few years and who’s dealt with client websites, just what they think of EIG owned website hosts.