"Did, or did not, Jesus keep the Law? Yes. Was Jesus impure? No. Therefore keeping the Law does not necessitate impurity."
What's your point? It is agreed that Jesus did not commit sin therefore His baptism was an identification and a sign. It was a voluntary obedience.
Mary's purification rite was different. She had a male son and the law said if a woman has a male son she has to undergo the purification rite to be part of the religious community i.e attend the sanctuary. It was not voluntary. She obeyed because her actions brought her within the Law.
(1) Keeing the Law does not necessitate impurity. (shown in 469)
(2) Mary kept the Law.
Therefore
(3) Mary's keeping the Law does not necessite any impurity in her.
-A8