Not headcannon, this was confirmed by the seakings themselves in the Oden flashback. Not only that but the power to make allies out of everyone is why, in addition to his individual strenght is why Big Mom and Kaido are failing before their alliance even begins.
There only mistake was being too much of a pussy to become PK until Luffy became a Pirate. All of them including Blackbeard are 100% pussies. Only Whitebeard, Roger and Shanks aside from Luffy had the balls to do whatever they want.