API changes breaking BC feel like they should be using versioning. I don't see enough people putting versioning support in to their API stuff at the outset. I've been chastised for doing that with "YAGNI". And then... one day, we do need it, and trying to introduce versioning support becomes... that much harder.
The context here was a class API, not a REST API, so versioning is not relevant.
You're right... misread that.
Does seem like you could namespace classes in to versions. Then it's much clearer which version of a class a caller is using.