The 8GB in his example is internal memory, used only by the phone to store the Android system image and application packages. All user data, including videos, are stored on the SD card, external memory. The vast majority of users will never install enough applications to fill internal memory, hence the OP's point is relatively moot.

I assume the author probably bought a dirt cheap Android device that doesn't actually have a decent amount of internal memory; my original G1 for instance only had 512M of internal memory, and installing some big apps or games could quickly fill that up. Modern, powerful Android phones can have 4G or more of internal memory for installed programs, which most users will never have a problem with.

Granted, I'm not saying this still isn't confusing, but for most people it should be a non-issue because the only thing they'll care about is filling the SD card.