Remember when Voldemort struck down Harry Potter in the series' finale, and then Harry woke up in a heavenly King's Cross station, where he met Dumbledore and learned just how f**ked he might've been?
Yeah, well this fairly decent theory from Reddit user WippitGuud, claims that Dumbledore was just spitting lies. Read and make of it for yourself:
When Harry was in Kings Cross in his head, he could have chosen to move on. Which means he was dead. There was some other force at work which gave him the choice to return to life, without needing the methods Voldemort had to use to create a new body. And Harry had something of that level of power with him - master of the united Hallows: he had the stone and the cloak, and the curse was cast from the Elder Wand, which he was currently master of.
Because Harry chose to not defend himself, the Wand was not defeating Harry, so its allegiance did not change. Dumbledore even comments on it, "And that, I think, will have made all the difference." Had he tried to duel, he would've lost allegiance to the wand when he lost, and simply died.
Dumbledore lied to Harry. Probably to protect him — knowing you're the master of the Hallows could make anyone power hungry.