@fossette, I don't know for sure but I suspect it was just mis-labeled.
You are right that there is more than one MAC associated with each device but since they go to the bother of marking the MAC on both the box and the Onion you would think that would be the one you need first to enable setup, in the case of MAC filtering. I have not investigated the others yet.
Hi,
Just a word of warning to others. I received my Onion Omega 2+ this morning and was having difficulty during setup in connecting it to my WiFi network. I have MAC filtering turned on on my router and had entered the MAC address from the Onion into the router safe list.
Eventually I turned MAC filtering off and the Onion connected right away. When I checked the MAC that the router had received there were two digits that were different than what was printed on the Onion.
Beware! 
Gib