So then the question is why can’t others remember? Blue Fairy, Rumple and Ragina all remember. August knows because he is from FTL but we don’t know who he is yet. Jefferson knew and disappeared into the hat. That makes 5 people that know the truth. To me that is a fair number. 6 if Nova remembers.
Are those characters cursed to not tell the truth because if that is the case the Blue Fairy is going against what fairies do. Rumple said “You’re lying!” and she said ” We don’t do that.”
I’m thinking that all of these characters possess magic. So perhaps there was something in their magic that kept them from having amnesia when the curse was enacted, or allows their memory to be triggered with the right catalyst, sooner.