The Pacifier came up in the UC Defense Manual bonuses too (SF1Edit), which makes me think it's either a double-dipping bug, or that this shotgun is an Allied Armaments gun instead. This's difficult to test, so I'm just gonna put this out there for someone else to futz with.
Well, with the Creations, Bethesda made a few themselves. Two of which are skin packs for the weapons. Allied Armaments get a Desert Camo skin, and Combatech gets a Digital Camo skin. The Pacifier only gets the Desert Camo, so apparently it's an Allied Armaments weapon.
Also: You can also get into the Syndicate's hideout via Novice level pickpocketing and a jetpack. There's an alternative entrance on the roof of Frankie's. I think this exit is opened by the key next to the magazine, but it does serve as an alternative way in.
Combatech weapons include: The game's best all around rifle (the Beowulf), the game's best Sniper (the Hard Target), and the game's best shotgun (Big Bang). Definitely well worth getting buffs to.
How you feel about the Fallout 4 Next general update I can't wait for free. New creation and putting in the game. Old creation I really want to buy hellfire. But now I realised is better just to wait for the update.