It's irony at its highest that you're advocating progression - the argument being that if the description is in use then that somehow makes it valid - and yet here you are pointing out how a standard that hasn't been observed causes this problem with capacity rating description of a battery.
I'm only aware of Amp-hours and milliamp-hours relating to battery capacity. There is no MegaAmp-hours. But you know, that's because I follow the standards.
20,000,000MAh should read 20,000,000mAh, which of course simplifies to 20,000Ah. That would be a hell of a battery. More correctly, it's likely that the battery is 20,000mAh. These kind of screw-ups are just what happens when one follows the idea of an anything goes progression.