By the way, does anyone have any idea why, as Jonah says, there is so little metacognition among mathematicians?

This isn't a complete answer, but I think a significant part of it is that metacognition is not incentivized professionally for researchers who are not at the top of their fields. Few pure mathematicians are capable of doing original work that requires a lot of metacognition. Still, there are question around why mathematicians aren't metacognitive anyway (professional incentives are not the only thing that drive people's behavior). I don't have a great answer to this, but my subsequent articles will shed some light on the situation.