While I agree the problem as written is ambiguous

It's not.

the answer pretty much always ends up being something along the lines of “well the experts do this” or “this professor at this prestigious university says this”, or “the scientific community says”.

Agree completely! Notice how they ALWAYS leave out high school Maths teachers and textbooks? You know, the ones who actually TEACH this topic. Always people OTHER THAN the people/books who teach this topic (and so always end up with the wrong conclusion).

while basic education and basic calculators use weak juxtaposition

Literally no-one in education uses so-called "weak juxtaposition" - there's no such thing. There's The Distributive Law and Terms, both of which use so-called "strong juxtaposition". Most calculators do too.

Shouldn’t strong juxtaposition be the precedent and the norm

It is. In fact it's the rules (The Distributive Law and Terms).

We should start saying weak juxtaposition is wrong

Maths teachers already DO say it's wrong.

This has been my devil’s advocate argument.

No, this is mostly a Maths teacher argument. You started off weak (saying its ambiguous), but then after that almost everything you said is actually correct - maybe you should be a Maths teacher. :-)