The release code words are just that: code words. They're not meant to represent some kind of underlying biological reality. OS X 10.1 was not code-named "The biological species Puma concolor", and OS X 10.8 is not code-named "The biological species Puma concolor".
The code-names "Puma" and "Mountain Lion" are distinct words, ergo they represent different releases. That in biology these words refer to the same species of cat is utterly irrelevant.
OSX 10.1 Puma.
Puma, Cougar, and Mountain Lion are names for the same species of cat (Puma concolor).