Take it from someone who's been through this -- at Moore's size, he should be able to lose 12 pounds in less than 12 days, let alone 21. If he can't lose 15-20 pounds in three weeks, he's not trying.
I agree with your analysis. I've also been through this, and he should be able to lose a LOT more than 12 pounds in 3 weeks. If he actually works at it, he should be able to lose 12 pounds in the first week alone.
Ive lost 30 since March, but I never lost more than 3 or 4 a week
ONLY when I did extreme hiking, 45 miles in 3 days with a high protein diet, did I lose more than 10 pounds in a week