Because it "Build fixes which cause a package to become compilable where it was previously failing", there is no PORTREVISION increment.
Poudriere testport Q/A include some warning but seems false warning (more detail in the PR exchange).
This is how I interpret this patch: This patch fix build on some arch/revision. This mean building of this port previously failed on these arch/revision.
And in chapter "188.8.131.52. PORTREVISION" of the porter's handbook, on the examples of changes which do not require a PORTREVISION bump, we found this point:
- Build fixes which cause a package to become compilable where it was previously failing
This is why I think we didn't need PORTREVISION on this specific case.