Seems likely that it is the same word originally (pallaṅka = paryaṅka).
I think the different translations are required by the context, not by the wording. If you “consent to the touch of heels”, you can’t sit in full lotus, because your heels cannot touch any relevant parts. But if a snake crawls around, the only way to access your vagina without having to go over your legs first is that you sit in full lotus. Then the snake can squeeze through small gaps between the ground and your legs.
But the content of the rules is obviously contradictory. In Pali, the cause for the laying down of the rule is that the heel is touching the vagina. In the Mg, the Buddha asks the nuns to sit like this.
It does seem that the purpose of the rule is quite unclear. In the Pali version, the rule which is laid down does not address the original problem. Even in half cross-legged position, you can still “consent to the touch of heels”. In the Mg, the origin story is a little far-fetched, so it’s unclear why the rule was laid down in the first place.