Chain of thought is essentially a recursive architecture. In its current form it a way to "debug" the reasoning process. This moves the cot process back into the transformer itself, thus never being exposed.
Like trying to find a bug in a recursive function that has no logs or breakpoints.
My (layman) understanding is, that currently there is a way to monitor the "thoughts" of the LLMs and that by looping more you lose that ability. The danger is presumably an AI that escapes human oversight.