There seem to be about 50m in wallets on bittrex. Pretty surely it is a mistake as you say, since it has already been said by that group that their coins are HMP, not THC.
Hard to do accounting properly when you are taking bong hits.
I will post this evidence about Cannabis Sativa, INC holding $THC in the HMP bitcointalk thread. Cryptocoins are crazy, maybe $HMP is a complete scam.