Thanks for pointing that out, the code has been changed.
At the same time, I can’t really imagine a case today, or in the foreseeable future, where gestaltSystemVersionMajor wouldn’t be 10 when queried from Cocoa code. I don’t know of any Cocoa code that targets OS 9. And if gestaltSystemVersionMajor was > 10, I somehow don’t think I would be using Gestalt() anymore.
In other words, it seems like verifying gestaltSystemVersionMajor is a waste of time. There’s nothing wrong with doing it though (besides an extra 1-2 lines of code). At least that’s my understanding.