Cancelling out of a submission which has already been initiated is not the only way a submission transition can be used to work towards a better position. Having an additional transition increases the chance that your opponent misreads the transition and denies the wrong direction additionally submission initiations can also be feinted.
In general I agree with you that we should have the D'Arce in more positions. During a given development cycle we have a limited number of time slots in the motion capture studio so we always want to capture the things that will deliver the greatest improvement in the gameplay experience, sometimes that's a new grapple position or submission, other times it's a new standup striking set. I think the additional D'Arce chokes have typically fallen on the losing side of the "Players want A but players want B more." discussion. However those items typically make their way to the winning side eventually.
Regards
-TOS