@Aretheus : it doesn't just show him an alternate past. He is actively overwriting him.
By making him revive the past "as it should be" he is erasing the previous memory and thoughts patterns of the prince.
It's near like killing him... Sure the body stay the same but a person isn't defined only by his body, without the memory and way of thinking as before it's not the same person anymore.
It's like if I showed you a person looking like your SO, just (s)he doesn't recognize you, act completely differently and is dating another person. Would that be okay because, by all purpose, your SO was with you only because you influenced her, the other isn't a fake, she just meet and dated another person.
And you can try but you'll never get your SO back because she doesn't know you and love someone else.
That what the spirit currently does and he does it for something he is persuaded is ultimately good.
Maybe you trust in "fate" and such, but in this case there is no "other prince" there is only one and deviation from the fated one isn't possible. It's understandable but then the bird is the agent of fate and is the one redirecting the prince to the fated route, making him lose all emotional progress he did and separating him from Bertia.