What I've determined from my own testing, is that the mounted grenade launcher counts as a separate weapon with its own flashlight/laser settings, even though the flashlight/laser aren't mounted to the grenade launcher per se. So if you want these attachments off, you have to turn it off on the weapon, then switch to the grenade launcher and turn it off there too.
The desired behavior is that the mounted grenade launcher should automatically inherit attachment settings from the weapon it's mounted on.
Yeah, I've been switching both every time I need to, it's just a huge inconvenience and time spent not being able to react as quickly as you need to. I don't see any reason why the settings ought not stay the same between the main weapon and the mounted GL.
