I don't disagree it is different. My argument was that a new release of compiler for an obsolete standard doesn't cause the standard not to be obsolete.

I am pretty sure there is theoretical way to run Python 2 code alongside Python 3 code, but they simply decided it's not worth the effort.

Edit: I think historically Python 2/3 divide is more akin to Maclisp/Common Lisp divide, but in the latter, the situation was even more complicated. But I doubt you can just take Maclisp code and run it on Common Lisp implementation, despite that fact that it was meant as a successor.