There is no strict rule that MHRB can't contain more than 1 % DMT. It is uncommon, yes, but your friend has apparently just been very lucky! To obtain such a yield, the strain must be very good, the growing conditions next to perfect, and it would also have to be harvested not to long ago. That is alot of conditions, so your friend are one lucky guy!
The crystals sounds reasonable pure, but you could perhaps try a recrystallization if you don't like them waxy?