I mean, arithmetic order is just convention
Nope, rules arising from the definition of the operators in the first place.
not a mathematical truth
It most certainly is a mathematical truth!
But that convention works in the way we know, yes, because that’s what’s… well… convention
The mnemonics are conventions, the rules are rules
So are the laws of nature, that Maths arises from
No, you making false accusations against Mathematicians is a strawman
You can change the conventions, you cannot change the rules
Nope, law of nature. Even several animals know how to count.
And you end up back where you started, since you can't change the laws of nature