Is the role of rogyapas in sky burials considered unclean by Tibetan Buddhists?

I just came across a Reddit comment referencing the Human Planet documentary about sky burials, in which there was an implication by the narrator that the rogyapa (body-breaker) performing the ritual must be a non-Buddhist (around 2:40). The Reddit comment states that breaking the body apart is a form of defilement, thus not appropriate for monks. Is this true, and is there any basis in Buddhist literature supporting such view?