> But if you really think it’s important, then you can consider a series of sizes like tabloid, letter, and memo to be equivalent to A3, A4, and A5.

This seems like you entirely missed the thread? The whole point is that this actually works for the A-series and in your made up US series it can't work because the ratio is wrong.

These are not made up sizes. They are standard paper sizes available in any store. Most ordinary househole printers won’t actually print on tabloid, and some won’t print on memo, but all copiers (and multifunction scanner/printers) can copy two letter pages and print them side by side, scaled down to memo size, on a single sheet letter of paper. It’s just a button you press, or maybe a checkbox you check, or whatever. It’s not magic.