The whole thing about sets and repetitions were created by bodybuilders in the 80s.
Most of it has no science behind it.
Exercise is exercise.
Does it hurt to do sets?
No, it doesn't.
But there are better ways of exercising, like high repetition and avoiding all intervals during a session.
I think that not even a second should be wasted during a session.
Never rest during a session!
For more tips, read my books available on this website.
Here is the old exercise paradigm.