In reply to Nick.

Since when WP autoupdates MAJOR versions?

It does not, though there were some discussions about that.

Some hosting providers might already do that for their clients.

Until now, if I’m correct, WP only autoupdates minor releases ONLY

Correct.

HAVE all the available ways to disable autoupdates are already been removed with 4.9.8, .7, etc…

No, using a plugin or a wp-config.php constant to control autoupdates should still work in any current or future version.