The great thing about a promise to be compatible is it means if it does break your build you know where to report the bug, and help out the developers who were

The great thing about a promise to be compatible is it means if it does break your build you know where to report the bug, and help out the developers who were trying to make a compatible release for your benefit. And that doesn't have anything in particular to do with semver at all. It is just about your use case and if you need to pin your dependencies or not, and the downsides to either approach.