It was discussed long ago in the original roadmap for the HF (in the comments, which is where the elimination of the quasi-linear curve got discussed and decided on) and the removal of this curve has been further discussed in official posts by hiveio, I'm fairly sure.
The release notes were written as a set of quick "one-liners" to point to relevant code changes, and are really focused on communicating with devs who might want to review the code changes. By one-liners, I mean they just very briefly discuss the idea attached to the change, with the expectation that the reader will follow the link to the merge request to gain a complete understanding of the associated change.
In the case of this curve removal, removing it from curation implicitly meant it was removed from the voting impact on author rewards too (otherwise, we'd be changing the reward sharing balance between authors and curators).