Only SI proponents use MiB from what I've seen.
Only scientists, engineers, and people who want to retain the existing definition, which was codified as an international standard long before computer geeks noticed that 2^10 is a tad more than 10^3, and copied the 'kilo' prefix FROM SI.
When I'm bitching about people butchering English, I draw a distinction between new words, or old words gaining additional meanings that don't contradict the old meanings; and the corrosive effect of a new meaning that opposes an existing meaning.
One of my peeves is people using a word like 'comprise' to mean the opposite of what the word traditionally has meant. This threatens to make the word meaningless.
When there's already an established meaning of SI prefixes, people deliberately misuse those prefixes to mean something else, and then have the gall to say that people who are using them as actual SI prefixes are 'false', we've gone through the looking glass and are having tea with the Queen, the Mad Hatter, and Humpty Dumpty.
HD manufacturers all use the SI meaning, because it allows them to advertise a larger number of MB.
Exactly. False advertising.
No, it would be suicidal for an HD manufacturer to use your definition of MB or GB, because it would make their drives look more expensive than competitors' drives of the same nominal size. There is nothing false about using the M and G prefixes in accordance with international standards.