huh? Mrd, Brd, Trd, ...

> it names adjacent intermediate orders of magnitude with only subtle mutations of the previous name

million and ten million are also rather close. So what?

> it's inconsistent with itself (<x 10^9)

Those are explicitly named for historical reasons, which is well in line with how names for numbers are handled: we generally work in a decimal system, yet have "eleven" and "twelve", followed by lastdigit-teen while everything above twenty is decimaldigit-y-lastdigit. (German has similar quirks, although the order remains the same. Still: neunzehn, nine-ten vs. neunundzwanzig, nine-and-twenty).

And let's not start with French (ten, twenty, thirty, fourty, fifty, sixty, sixty-ten, four-twenties, four-twenties-ten, hundred). [to be fair, Switzerland and Belgium fixed that in their dialects, using septante, huitante, nonante]

> in 2019 it's extremely ambiguous

It was ambiguous since the 17th century when the short scale was invented.

I'm not sure if the UK officially switched by now, all I see is a random statement by a Prime Minister 45 years ago that I'm not sure is normative (https://api.parliament.uk/historic-hansard/written-answers/1...)

> in all languages SI prefixes have been around since 1960

Sure, and it's used sometimes, but are SI prefixes defined as normative numbering scheme anywhere? That is, which language and which country uses Gigagrams officially?