What on earth are you trying to say here? Are you saying that speed-breeding contributes to failures? Or that waiting it out mostly results in failures? You seem to be saying both, although NEITHER makes sense to me.
When you tap the breed button and get a timer, the specific breed is already set. One 18-hour animal cannot turn into another. The success or failure is apparent as soon as you get the timer in most cases. For speed breeders, failure is usually a foregone conclusion; they KNOW that what they are speeding out of the Garden is something they don't want. They are speeding their unwanted breeds to have an immediate opportunity to try again.
In this particular case, there are two animals with the same parentage and breeding time, but that only presents the question of whether one is speeding a Bansheep or an Elephantom. Whichever it is, the decision to speed or wait cannot possibly change it. The system cannot read your mind. After all, you may be TRYING to get an Elephantom or even the Koala.