I'm going to take a stab at it and others can correct or add in.
BH is the distance from the back of the grip to the string at rest. The shorter the distance, you'll loose accuracy due to the arrow staying longer on the string when you release the trigger. That means that more likely your bow hand might move slightly before the arrow depart from the string.
IMO, I think this is more on the shooter. If you have very good form, you'll do fine with lower BH. Also, I think lower BH affects longer draw length shooters than short draw shooters.