You could refuse the offer, but look like you felt for the trick... If this is a fraudulent scheme you became an accessory for their criminal enterprise
This is uncalled for. Biomech didnt ask a thing, and got offered a free miner. No one should be expected to refuse that based on a hunch this might be a scam.
I would however, be careful not to put too much weight on the results. Not that i have reason to suspect Biomech from being untruthful, its just that the ability of anyone to cram a few off the shelve technobit boards in a standard mATX case was never in question.