The use case would be something similar for the messages and signals. If you are able to query the jobs by the id of the timer you would be able to get the exact job you need. I cannot explain a lot, but imagine that one wants to execute a job only for a specific timer depending of it's ID, one reason for this can be when someone wants to bring a process Instance to a certain state by replaying some actions. It is better to manually execute the job than to mess with the System clock so the job is executed by the job executor. This can also be used for testing the business model if it behaves as it should be, for example if you have multiple active timers, but you want only one of them to be executed.
This is only my opinion, maybe you would disagree with me.
