He knows more than a little. He has been doing Judo since he was 6 and was considering going to the UFC for a while before he made buckets in arm wrestling and trained MMA for a long time. Dude is 6'6, 80 inch reach, 270, judo black belt, been the equivalent to a Canadian NAVY SEALS for decades, trained in MMA for decades, competitive and tough AF....should be a fun freak fight.
Like you point out, Thor's cardio may be suspect. Devon has never lost a long battle in arm wrestling and his specialty is drawing out and bleeding his opponents, kind of like Diaz in MMA. Will be interesting how that cardio and tenacity translate vs a guy who will be larger and been doing straight boxing for a while. Thor is a big and strong guy but he does not seem to be a fighter.