To me the Label seems like the right address… the “actual” you mention shows really only a manufacturer portion of an address, the last portion is the unique adapter address.
So the answer to 1 I believe is yes, they should match.
For 2, it is typical for some portion of the ethernet network components to supply a MAC address. It is done to give uniqueness. (there are some hardware providers out there who do not go to the expense of doing this which can leave an end-user to guess and hope they don’t conflict with an existing device).
I don’t know whether the Mountaineer boards are meant to fall into the category of supplied unique addresses or not; lets see if one of the mountaineer team can answer that. What I can say is that 0050C2 seems to be the “ieee registration authority” MAC address vendor.
I don’t know what the behaviour of MFDeploy on this board is meant to be, but perhaps it’s not possible to set MAC address via MFDeploy. I suspect that has to be set up when the firmware is created, so it may not have been done.
One more way of getting a unique ID for a board is to use a OneWire device connected to it and use it’s address as the ID.