Still, being able to alter the past of someone that is near you is not small feat...
Wylis was no dim witted, so Bran can do it with anyone.
Maybe he must be near a sacred tree to do it, but still it's a terrifing power he has, being able to completely erase one's actions from history.
I would like to give the credit for such a bad writing to D&D, but I fear that this was Martin doing.