if you’re trying to bluff yes, you probably could just do this with a deception check. but I think this is different because you can use it to retroactively affect the narrative of an NPC. The deception check you’re making in that case is to successfully convince them throughout their life that you were just the buttler or something.

A creative GM might let you do that normally if it’s within plausibility and you clear it with them first, but having a distinct feat and ruleset to do that is unique and helpful.