If a CPL holder has only experienced training environment stuff, to the point where they "can count the number of off-airfield landings they have done on one hand", does becoming a baby instructor really help that much? You get some more training, specifically aimed at how infant pilots will try to kill you, and I bet your reaction times and awareness improve, but you're not really adding new experiences, right? You're still mostly flogging around the circuit and local area, only now you're (nervously) watching someone else do some of the flying.
Just sayin'...