I'm saying that the fact that it is (apparently) the norm in JavaScript-world that authors will regularly publish breaking changes that are not advertised as such, and that that is just an acceptable everyday uncommentworthy inconvenience, is surprising to me. How do y'all get anything done if you can't even trust SemVer enough to automatically pull in minor/patch updates to dependencies!?
In my experience the most common cause of breaking changes is accidentally breaking on older versions of the runtime, because the project is only running tests on the last version or two. Aside from that, the only notable example I can think of in the last year was a pretty subtle bug in what was supposed to be a pure performance optimization in a query language [1]. I think these are pretty representative, and not meaningfully worse than the experience in other languages.