If you integrate your code to have hard dependencies on a third party server that is provided for free, that's as much part of an implicit social contract as is channeling a subset of earnings back at a project if you're successful. So it may be okay in this instance, but the no notice part is still bad.

WordPress used to not even have a way to have plugins and themes that didn't ask to be updated via WP.org - so you could provoke an update to someone's private plugin if you knew its name. I know because I filed the bug that lead to it being fixed.

But everything in this instance is making Matt and his company look bad. Their complaint seems to be that revisions are not enabled by default on WP Engine and this is somehow breaking the core philosophy of WordPress and the few bytes of text WP Engine saves are supposedly profit seeking, not a performance problem as WP Engine claims.

Additionally, one of Matt's commercial ventures, Pressable, is currently offering to buy out your WP Engine contract if you switch to them. Breaking a competitors product and then offering to buy out their customers should be a red flag in choosing an open source solution.