There are two types of weapons that have "Scimitar" in their names, on is a "Talwar/Sapara" model, the other a "Cutlass" model. PLD, outside of rare cases, cannot equip either of these model types. Generally its THF/DRK/BLU/COR/BST(RNG and SAM being common too), but sometimes more, including PLD.

"Corsair's Scimitar" a Talwar/Sapara type model.
http://www.ffxiah.com/item/16551/sapara
SS:
http://www.ffxiah.com/screenshots/42523

"Senior Muskateer's Scimitar", a Cutlass type model.
http://www.ffxiah.com/item/16560/cutlass
SS(Ridill):
http://www.ffxiah.com/screenshots/561

Its odd honestly, they occasionally throw the basic job on these types to the wind, and othertimes not... I think this situation should have called for throwing the basic job things out in favor of putting PLD on one.