I thought that was the accepted definition of ???? ??? ????. Do you have a different definition? I am not claiming any level of expertise on this topic.
Accepted by whom, and why? I assume it was defined that way based on the scientific beliefs, but who says Chazal meant that? They meant it doesn’t fit the halachic definition of parah v’ravah, not the scientific definition of reproduction. Sort of how a pri isn’t always a fruit.
I don’t know what this means. If a cow gets a disease that would have killed it within 12 months, but we give it Penicillin and it lives, is it now a treifah?
Assuming in the times of Chazal there was no known cure (and the illness fit one of the categories listed in the Mishna and B’raisa), it would be a treifah.