I don't think they are making up arbitrary rules, I think it's problem solving. Brainstorming alternative solutions that are cost effective and solve the problem is a useful exercise. We shouldn't just blindly use machine learning because it's there.

Honestly, despite your facetiousness, this is the best starting point. And then from here work up to more complex solutions if there are reasons why rhis simple one isn’t suitable

This wouldn't work as there is a time requirement of 20 minutes. A solution to this would have to be real-time and not require one to manually log their presence, which would defeat the whole point.