So then why did they mention Grenade Launchers at all? The make it a point to specify that you can reload grenade launchers...which if they didn't use grenade rules wouldn't be needed, as you can reload any weapon unless it has scarce or limited. They took the time to spell out how grenade launchers differ from grenades which implies they don't differ from grenades for some of the rules. The logical step is that they use the grenade rules as written except where specified, since this is a game that lists general rules and then exceptions. The exceptions in this case are being allowed to reload, slightly different ammo check numbers, and different ranges.That's all it does. If a weapon needs to use those rules, there is no reason not to give it the Grenade trait. Therefore, weapon without this trait don't use those rules.