Having the PR issued from a feature branch makes things much easier, e.g. with editing the pr. So it is a strong recommendation.
But the source branch makes no actual difference to the code quality or the commit contents. Handling Ng that as error seems too harsh to me.
Please convert the "from master" error into a warning.
Example
https://github.com/openwrt/packages/actions/runs/21026058778/job/61403662110