When a workflow is tied to a github environment, it may have approval rules that need acceptance before it can run. Unfortunately GitHub webhook / API is not great with regards to getting the true status of those jobs, so RunsOn prefers to wait a bit more so that GitHub internal state eventually converges to the "true" state (queued, or still waiting for approval). This is why you can see up to ~20s delay.

This should be improved, probably doing an addition check on pending deploys for the run before enqueuing.