Wolf,
No, not based on actual observation, because they generally only saw the defect after the animal died.
Obviously, if a high percentage of animals which had a visible halchic defect lived more than a year, that would make the position of “treifa eina chaya” untenable. Since you likely agree that Chaza”l weren’t simpletons (although we might disagree about their infallibility in matters of metzius), I think we can assume that this is not what occurred.