Whenever I’ve been on the hiring side of an interview, the people seated in the interview aren’t given any special “Keep the company safe” training, but the HR person coordinating always have been. I suspect that’s why it works much better to ask in the interview than after it.
Systemd is trying to stop a service. To do an action to a service (or any unit), it runs a job. The job to stop a service is called a stop job. Once the stop job is taken off the job queue, the stop job is running.
The method of stopping a service is configurable, but the default is to send a kill signal to the MainPID, then wait for the process to exit. If it doesn’t, after a timeout, the kill is reattempted with a harsher signal.