Maybe merge-queue bug. In https://github.com/WebKit/WebKit/pull/279, it uses merge-queue to land it. While patch is landed, PR is closed instead of merged (red badge instead of purple badge).
TLDR, blame `git-svn`. Merge-Queue does it's best, but it's racey. I'm not going to be putting any effort to improving that situation, it will be better when we aren't backed by Subversion.