[ports] Shouldn't we rebuild all dependant packages whenever a library changes?

Hello!
I stumbled across a strange glitch and not for the first time. Did a pkg upgrade, which updated Qt (new minor version). This breaks all Qt apps installed via pkg since they were built against a different minor version of Qt, but were not rebuilt and pushed to the repository along with Qt.
Qt checks the library versions on startup, so you notice this immediately.
The current behavior (or lack of behavior) however could affect __all__ applications, even those that link only against plain C libraries. It's rare, but you can't exclude that some minor library release breaks the API - ABI is of course not a problem in C, compared to C++.
Workaround is to (re)build the corresponding application manually from the ports tree. This can take hours, so IMHO this is a serious issue.
It is NOT sufficient to reinstall the package in question - it obviously didn't change in the repository.
I would therefore think that every library change should result in a rebuild of all dependant packages and automatic bumping of the package version.
Why is this not done? And where should we file a bug report?
Best regards,
Robin