I'd rephrase: it's ok to monitor that the jobs are being performed, and sometimes this involves an employee doing something in a certain place at a certain time.
Though highly-overlapping, this is not a 1:1 correspondence with "tracking employees."
You may need to know that a security guard visited this station at 1:00 and this station at 1:30. You do not need to track whether he was in the bathroom five minutes longer today that yesterday.
A real guard needs to run a somewhat random schedule, otherwise attackers will figure out the pattern. I don't need to know how long you spend in the bathroom (unless it is excessive), that is just data that I happen to get by tracking to ensure there is enough randomness in your patterns. It should go without saying that guards need sufficient time to handle biology needs, and this varies a bit.
If you are so high profile that attackers are trying to profile guard movement patterns, you need more than 1 guard, and they can take turns using the bathroom.
An app on a personal phone can violate this way too easily. The tagging system is a good way to do it and limit it to only being on the clock.