You defined speciation as the point at which 2 organisms can longer have a healthy offspring. I was pointing out your cutoff point is a bit off, that while horse and donkey can produce a mule they are (already) 2 different species. In other words, speciation comes at an earlier point than at the scenario you described.
Don't change the issue... The topic was: how to define speciation. Not which species can have sex with which species.
Sent from my iPhone using Tapatalk