If the units are different (e.g. a percentage and a number, or a number and a currency), a second scale on the same axis is basically a must. Also, I can't recall ever seeing a real graph break this rule and put two scales on the same axis when the units were the same. As such, calling it out in this guide might do more harm than good.

Part of the point with 3 is that it assumes whoever made the chart has access to the data going back much further, meaning they knew the last few years are not representative of the longer trend. By only showing the last few years anyway, they're deliberately misleading people.

Maybe it's not always intentional, but as journalists they have an obligation to do it right.