The question to be asked here is what a breaking change in the API means for the business use case. Is the application's past behavior not valid anymore? Should the client have to stop working from now on?

This is equivalent to, for example, a vendor of a widely-used smartphone app that decides to break existing versions and to force the users to update the installations to its latest version. There is arguably no need in doing so for existing functionality to continue.

If for some reason the existing use cases can't be used as is anymore, some additional, compensating business logic should be considered.