[wging]

Not all changes result in a change to the way your service is called, and even those changes can (with some effort and care) be made backwards-compatible. Performance-level changes are one obvious one - for example, I wouldn't expect to have to keep my caller in the loop if I decrease my API's latency by 50ms, even though it might be a good idea.

But other behavior changes are also not necessarily something that requires a team to be alerted. A good design provides an abstraction where the caller shouldn't have to care about the underlying implementation or details of how a request is fulfilled.