A unit change passes through three places, and at the start of the lesson it got stuck in the first. This step shows what daemon-reload does with it.
The first place is the file on disk. The second is the description loaded into systemd: systemd starts the service from it and prints the status summary from it. daemon-reload carries the file into the description. The third is the service's running process. See what daemon-reload does to it on lab-worker, whose file has a changed service description, Description.
Reload the description
See which description (Description) and which main process systemd knows for lab-worker, reload the unit files and read the service summary.
First, predict
What will the status summary show after daemon-reload?
Now start the exercise, run the command and compare your prediction with the output.
systemd updated the description at once, while the process stayed the same. The lines the process is started from, User and ExecStart, reach only a new process. That is why a service is restarted after such lines change.