GitHub checks doesn't display any information about pending builds for a PR. It only shows information about completed and in-progress build, but absolutely no information for pending builds. It's possible for GitHub check to say "All checks have passed" "4 successful checks", even though the PR is waiting on many other queues (on which it might fail). Noticed this in one of my recent PR in which GitHub checks says "All checks have passed", even though the PR has pending build-request on a buildbot queue which is backlogged.
That's another reason to implement our custom solution for EWS UI on GitHub.
<rdar://problem/88309423>
Yes, this is a known limitation of our current approach. I think having ews.webkit.org own updating GitHub will improve this situation, but unless ews.webkit.org is going to receive hooks from GitHub, I don't know that we'll ever be able to completely solve the problem.