I found out that they do not automatically adapt to JIS sizes. My wife’s work once had a printer that somehow got configured to use JIS, I assume JB5. It then refused to print on US Letter, but as printers are wont to do, didn’t produce any useful error message, nor relay this information to the computer. It just wouldn’t print. I only discovered this (because if you work in tech, you must know how to fix printers, right?) by laboriously scrolling through every menu on the tiny LCD screen, and finding that the paper settings were incorrect.