I think it is one dictionary authors would agree with? Dictionaries do not dictate the meanings of words; they document them.
Now, within some contexts it is best to stick to standard precise definitions for some words. Still, the meaning of a word within a community is determined by how it is used and understood within that community, not by what is in a dictionary.
Not always. Where I come from there's very strong push to speak the standard language, and regional variations are simply considered wrong. This leads to situations where words commonly used across the whole country don't make it to the dictionary because of petty office politics of those who make dictionaries. Changing the dictionary to allow things previously considered "wrong" would damage the reputation of scholars, who pride themselves in being exemplary.
Now, within some contexts it is best to stick to standard precise definitions for some words. Still, the meaning of a word within a community is determined by how it is used and understood within that community, not by what is in a dictionary.