jenkins.branch.Branch#getName uses head.getName
That ends that branch name equals PR name makes branch api crazy.
As example your github-branchsource-plugin https://ci.jenkins.io/job/Plugins/job/github-plugin/job/PR-182/ after branch appeared in Branches it disappeared in PullRequests and mixined build history.

And guess revision https://ci.jenkins.io/job/Plugins/job/github-plugin/job/PR-182/5/

Normally SCMCategories must be part of branch names or at all subfolders. And the easiest: enforce implementations to deal themselves with prefixes (that ideally are categories).