Not sure why the downvotes here, a database service misusing semantic version is itself a red flag in my opinion. If major releases don't indicate a breaking change I'm not as confident in what might be part of a minor or patch release.

To be fair, they have a bunch of associated tooling like their query language and UI, so it might have been those that have merited a bump to 3.x

Yeah that could be, but I think that would still only merit the bump it there was a breaking change in the public API