When I was in school, year 7 was primary school

Oh really? My apologies then. I've only ever heard Year 7 called high school or middle school, never primary school. What country is that in?

multiplication by juxtaposition. Which I’m fairly sure for me at least was in year 6

I've seen some Year 6 classes do some pre-algebra (like "what number goes in this box to make this true"), but Year 7 is when it's properly first taught. Every textbook I've ever seen it in has been Year 7 (and Year 8, as revision).

Also, it's not "multiplication by juxtaposition", since it's not multiplication - it's The Distributive Law - which is Distribution - and/or Terms - which is a product, which is the result of a multiplication.

No, the idea of specifically codifying BIDMAS comes from the early 1900s

The order of operations rules are older than that - we can see in Lennes' letter (1917) that all the textbooks were already using it then, and Cajori says - in 1928 - that the order of operations rules are at least 300 years old (which now makes them at least 400 years old).

If you're talking about when was the mnemonic BIDMAS made up, that I don't know, but the mnemonics are only ways to remember the rules anyway, not the actual rules.

I don’t know why you’re going throughout this thread

I'm a Maths teacher, that's what we do. :-)

a rigid primary school application of BIDMAS will lead you to the wrong answer

Only if the bracketed term has a coefficient (welcome to how Texas Instruments gets the wrong answer), which is never the case in Primary School questions - that's taught in Year 7 (when we teach The Distributive Law).

juxtaposition actually comes before explicit multiplication... I think that’s what you mean when you keep saying “it’s called terms”

Terms come before operators, and we never call it juxtaposition, because The Distributive Law is also what people are calling "strong juxtaposition" (and/or "implicit multiplication"), but is a separate rule, so to lump 2 different rules together under 1 name is where a lot of people end up going wrong. There's a Youtube where the woman gets confused by a calculator's behaviour and she says "sometimes it obeys juxtaposition and sometimes it doesn't" (cos she lumped those 2 rules together), and I for one can see clear as day the issue is it's obeying Terms but not obeying The Distributive Law (but she lumped them together and doesn't understand these are 2 separate behaviours).

Terms and multiplication by juxtaposition can work together

But that's my point, there's no such thing as "multiplication by juxtaposition". A Term is a product, which is the result of a multiplication.

If a=2 and b=3 then...

axb=2x3 - 2 terms

ab=6 - 1 term

In the mnemonics "Multiplication" refers literally to multiplication signs, and nothing else. The Distributive Law is done as part of solving Brackets, and there's nothing that needs doing with Terms, since they're already simplified (unless you've been given some values for the pronumerals, in which case you can substitute in the values, but see above for the correct way to do this with ab, though you could also do (2x3), but absolutely never 2x3, cos then you just broke up the term, and get the wrong answer - brackets can't be removed unless there is only 1 term left inside. People writing 2(3)=2x3 are making the same mistake).