Shotgun rounds for Pistols

[Rev Haus 235]

I know it sounds a bit crazy, but I didn't make the rules, or add these guns myself.
The Remington Roomsweeper is described as a short barrel shotgun pistol, and the Eichiro Hatamoto II is a single shot large bore shotgun pistol. The later will allow you to take any kind of ammo for shotguns that you normally would, however the former does not. Specifically I see that it does not let you take the Flare rounds, or the Shock Lock Rounds. It even specifically says that you can't take them because they are shotgun rounds. I'm confused, the Remington Roomsweeper is a shotgun, that's what the description says it is.
Should I be able to load any kind of shotgun round into the Remington Roomsweeper?

Additionally, how come the False Bottomed Attache Case isn't a container that can hold things? For that matter, shouldn't it be two containers? One for the false bottom, and one for the regular part?