I sincerely hope you never test this theory. I think many people in this thread are severely underestimating how little noise is needed to be disruptive in the early morning.
My local noise ordinance sets the maximum permissible noise in residential areas during off-hours (10pm - 9am on weekends) at 45 dB. That can be exceeded by 5 dB for 15 minutes, 10 dB for 5 minutes, and 15 dB for 1.5 minutes. Lawnmowers are an exempt source of noise during day hours only. I guarantee if you were my neighbor your mower would be in violation of noise ordinance at night.
Plus, assume some people are sleeping with their windows open. Especially in mowing weather. Windows open overnight may be the only way they keep their house bearable during hot days.
Another laziness by the professors is using book questions instead of just writing their own.
When I taught I told my students that the book was a resource for studying the material from a different perspective than the one I gave in lectures. Not actually required for the course even though I didn't have control over it being listed as required on the course listing. And I told them if they wanted to get it, they should find the cheapest copy they could. I've heard you can sometimes find very cheap electronic copies (wink wink).
It is funny to see the questions you write end up on Chegg though.