xkcd #3232: Countdown Standard
Title text:
Anyone who is caught counting ‘three … two … one … zero … GO!’ will be punished with a lifetime of eating only ISO standard food samples.
Transcript:
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Source: https://xkcd.com/3232/


Obviously for this case we need to add a signifier for the countdown so it’s clear to the other parties that you are aware of the standard and adhering to it before you even begin the countdown.
Like “ISO three two one GO!”
This is semi-backwards compatible, but still confusing for normies.
Even better, just make up new words where the ambiguity never existed. No numbers at all, just “glarp dook peow” and we always go on “peow” and always have. No backwards compatibility, but you’ll be guaranteed that a person who doesn’t understand will need clarification, and won’t go unexpectedly through imagined agreement.
Or, if backwards compatibility is required, we could count up from 1 to 3… and our signifier phrase could be something like “awnthree”. As a label for the standard we’re using! Like, “awnthree, one, two, three”.
I think that could work 😛
I do almost exactly this, but with random digits.
“Eight… Five… Nine!.”
It shows that the language matters less than the delivery.
I think you need a fourth word for better timing. A person might misinterpret the duration between glarp and dook, and arrive at peow too early or late. Just one more timing sample is better to reduce human error.
But do you start lifting on the pee or the aow?