Well, my understanding of the phenomenon is thus: a variable number of outcomes for event X occuring simultaneously leaves Akatosh hurting.
In Daggerfall,event X is the PC gifting the mantella and totally reworking Tamriel's geopolitical situation.
My hypothesis is that the variable gender and race of the heroes poses the threat of a similar paradox, if only of a lesser magnitude. Individuals, after all, are as much a product of history as anything else. The probability of a specific guy meeting a specific girl under the right circumstances to allow them to join in coitus is astronomical, not to mention the tricky business of gene expression that determines what their offspring will be like.
Also recall that TES's special brand of chosen-ones, as part of their continuing campaign to subvert fantasy clichés, seem not to have their lot determined by the circumstances of birth (i.e. were specifically, especially destined to fulfill the prophecy); but are rather distinguished by their actions. They aren't born the heralded heroes, but rather they become them. In this way they are simultaneously bound by fate and possessed of free will. Remember what the Underking said:
Each Event is preceded by Prophecy. But Without the hero, there is no Event
Moreover, I just think it's a much more compelling handwave than the milquetoast "...and then he rode off into the sunset, but we never did get a good look at him." excuse we've received in the past.