Sure, for small stuff that makes sense for a one or two time experience. They recommended 60 days. Eating preprocessed frozen diners for two months could be unenjoyable to one party and not the other. They might not care about the added cost too. So it could work if they try to stick to the rules. If they just don't care, then that might suck.
Then for the car issue... even one large mistake could cost thousands or lead to death. If they are supervised, then maybe that could work. But that would at least require enough extra time to allocate 2 resources to the same task.
Yeah, the way my wife and and I go about rotating tasks usually has one person explaining/hand-holding to whatever degree is appropriate precisely because damaging goods isn't a desirable outcome. As an exercise, it can still surface issues even without full on cold turkey switches, e.g. does one tend to forget/downplay/skimp things that were already covered previously, is the communication actionable/respectful/unambiguous/etc, do complaints surface verbally, does the taught person actually take away any lessons they didn't know/consider/appreciate before, etc.
For example, the junk food example doesn't need to literally put you in the red, it can just lead to you complaining the food is crap and hopefully imparting that food not being crap is important to you.
Then for the car issue... even one large mistake could cost thousands or lead to death. If they are supervised, then maybe that could work. But that would at least require enough extra time to allocate 2 resources to the same task.