Let's say that ALL of the jobs suddenly take up 6s. They ALL get queued up.
Now you have a queue problem and you have more to debug. You have to figure out why the queue is filling up and why things are taking longer than 5s. You also have an issue where the execution might die (machine crashes) before the job makes it into a queue.
You're better off just going straight to queue with the jobs and remove the added complexity of a 5s rule.
The 5s check is just there to improve UX on small user actions.