From the (very nice) link:

"There will be one release per year and it will contain all features that are finished by a yearly deadline."

That seems to be what is going on here with Python. Most JS implementations have differing amounts of the early stage features they have implemented, and given their open source nature some of the Python implementations can do the same thing.

I feel like I'm missing your point but to me it looks like the languages are converging on broadly similar release processes.