Where is the game_shortname used (in the game_information {} block) and why is it so restrictive - only 13 characters? Does it matter if I omit it? If I leave it blank, it doesn't complain.

The game shortname is restrictive as it is used for naming in a space constrained app list. It's also used as a key in the save game routine.

It's not technically needed but it's nice to have.