Can you clarify the concern? Starting from C I've come to expect many dialects across many compiler implementations. It seems healthy and encourages experimentation. Is it not a sign of a health language ecosystem?
Pypy compatibility with cpython seems very minor in comparison https://pypy.org/compat.html
It's a culture thing. C culture is all about rolling your own bespoke solution, which encourages the formation of dialects. On the other hand, Python culture is all about "There should be one-- and preferably only one --obvious way to do it.": https://peps.python.org/pep-0020/#the-zen-of-python