To be fair, it does appear that W and H rejected the substitutionary view of atonement - sometimes strongly and other times mildly. However, this is in no way heretical as the substitutionary view of atonement is by no means essential for orthodoxy (it doesn't even get formulated till nearly 1200AD). It is an "in house" debate and thus not a sufficient reason for division over a translation.
Rejecting the atonement is not heretical? Pray tell, what is????