I don't think that's right, or at least maybe not for the colonies.

I grew up in New Zealand and my mother was very insistent that I spelled and spoke "Proper English", rather than American English. This was before Microsoft Word was popular and the source of truth for the English language, especially for my tech-illiterate mother. She also didn't like me using slang, especially the Kiwi tendency to say "sweet as" and put "aye" on the end of sentences.

Maybe it's a colonial hangover, trying to hold on to the British identity, or maybe it's because she had a less privileged upbringing and saw "Proper English" as a sign of higher status.