For something as large as a printer, it makes perfect sense.
I use more mini-Bs but the micro connector is a better connector electrically. 'C' makes more sense if you're powering something over USB or you need video speeds, or some such.
As *A* serial port. Which one, no one knows. I've been putting the MicroChip version of the USB/Serial chip on my boards as a debug aid. They don't get populated in production but it makes it easier for the software types.