Does this theory explain what really happened when Harry Potter met the Dementors in The Deathly Hallows?

A Potter fan has a theory as to why the Dementors didn't effect Harry on his way to his battle with the Dark Lord, or during his return and it's rather intriguing...

As Harry leaves Hogwarts and heads for the forest to face his destiny, he doesn't experience the soul-sucking power of the Dementors that are surrounding the castle. He believes at the time that it's because he is protected by his father and the other Marauders, in the same way that a Patronus might ward off Dementors. But we soon learn they were not actually present but only there in Harry's mind.

When he returns after his battle with Voldemort, the Dementors' power is also ineffectual. But why?

Reddit user LastBaron argues that Harry, now in possession and control of the three Deathly Hallows – the cloak of invisibility, the elder wand and the resurrection stone – has become the prophecied Master of Death. The theory is that since he is mentally prepared for death, and no longer fears it, the Dementors have no power over him.

As one commenter put it, "Dude yea. I bet they feed off the fear of death by the thing you fear most".