Hey, you're right, Cajori does talk about operator precedence.
Unfortunately, it talks about how the rules, especially for mixed division and multiplication, have changed over time. Supporting my point that these "rules" are not in fact rules of maths, but instead rules of mathematicians.
That is why Cajori includes them in a book about the history of how we write mathematics. No matter how you write multiplication and addition, they must always be commutative, associative relations which obey the distributive law; if they didn't, they wouldn't be multiplication and addition. However, you can write them down in different ways, by using different symbols for example. Using different symbols for multiplication changes what a sequence of mathematical symbols means, but it doesn't change what multiplication is. Doing the operations described by a sequence of mathematical symbols in one order or another order may break one set of rules of precedence, but those are rules made by mathematicians not by the fundamental working of the universe.
How do I know this? Because Cajori says that, at the time he was writing, there was "no agreement" over the order in which to perform divisions and multiplications if both occur in an expression. So here's a question for you: do you agree with Cajori that at one time there was no agreement over which order to perform multiplications and divisions, or not?
If you do agree that there was no such agreement, do you then agree that, for there to be agreement now, such as there may be, that change must be through rules created by mathematicians, rather than by rules given to us from the universe itself? Because the universe certainly didn't change in the meantime, did it?
If you don't agree then that would rather expose your fetishisation of textbooks as hollow trolling, of course.