While reading some of his linked textbooks I found examples which define the solidus as operating on everything in the next term, which would have 1/ab = 1/(ab) = 1/(ab) = 1/ab. This is also how we were taught though as I recall it was not taught systematically: specifically I remember one teacher when I was about 17 complaining that people in her class were writing 1/a·b but should have been writing (1/a)·b (we generally used a dot for multiplication at this point). But at this point in our education, none of us remembered ever being taught this. I suspect what happened was that when being taught order of operations some years before, we simply never used the solidus and only used ÷ or fraction notation.

Anyway, if you have a correct understanding of what the order of operations really are (conventions) you can understand that these conventions all become a bit unwieldy when you have a very complex formula, and that it's better to write mathematics as if there were no such convention in those cases, and provide brackets for disambiguation. Thus while you might write ab ÷ bc and reasonably expect everyone to understand you mean (ab)/(bc) not ((ab)/b)c (which is what the strict interpretation of PEMDAS would say!) because "bc" just visually creates a single thing, the same is not true of the expression ab ÷ bc(x-1)(y-1)·sin(b), even though bc(x-1)(y-1)·sin(b) is a single term, and so the latter should be written more clearly.

Because DumbMan doesn't understand mathematical convention, he doesn't understand that these things really depend on how they're perceived, so is incapable of understanding such a way of working.

Anyway, looks like he's gone to sleep again now, I wonder if he'll pop up again in a couple of days, or if it'll take him until someone else posts some BODMAS clickbait.