A perfectly healthy person can get a cold, need a day or two off, and then be back at 100%. I don't think a day or two off is going to take someone from the verge of a mental breakdown, to 100% mentally healthy. So they're not really equivalent.
Fuck this attitude. I've avoided burnout by taking short-notice leave, a day at a time. I have used it to get clothes ready for the next work day, cleanup house, take care of my dog, play video games, or pursue hobbies. It keeps my mental health at a reasonable level. Maybe not 100% but you can't really put a percent on physical health either. And it's easier to take one day to recover(going from e.g. 20% to 80%) than to need months of recovery when you do get totally burned out.