> Calling it an incompatible change is perhaps a little strong.

Definitions of backwards incompatibility are either tautological or disingenuous (provided we talk about documented behavior).

The right way to do that change would have been to allow both names without warnings in a point/minor release (with the docs stating where the project is headed), add the depreciation warning with the next semver major one, and remove the old name on the next next semver major release.