Well, yes - those AI tools output images in aspect ratios which are not those of a typical sheet of paper (16:9, 2:3), which indeed wont't match. "Inches" etc doesn't matter.

You just need to offer the customer either the options of scale-to-fit / fill / stretch (white borders / crop on two edges / stretch), you probably already needed to do that before AI (such as people wanting to print letter-size documents in A4 land).