I think it makes sense if you think about it. “Max” is pretty objective, it means the highest limit of something, so that’s the most powerful. “Ultra” isn’t very clear, but we know it’s lower than Max and higher than “not ultra”, so it’s in the middle. Since both “max” and “ultra” imply something not just better but larger, we can conclude that the plain M2 is the version targeted at more power efficient devices. Finally, Pro stands out as the only modifier clearly unrelated to computing performance, so it must have to do with “professional” features, like ECC RAM and MDM.