The parent is working with scouts for rank advancements. When it comes to working on advancements, our leaders divide the scouts into their ranks. Each group has a leader working with the scouts on their requirements for whatever rank they are working on.. This parent is one of those individuals.
This parent is also not registered as a MB Counselor and is teaching merit badges to Scouts (as a group) in our troop. Just as any registered MB Counselor would.
I believe you are allowed to have unregistered people help teach/assist MB topics as long as a registered MB counselor