Pan manipulates, but we don’t yet know if he’s prone to lying. He has said he always keeps his promises.
Rumple was the one who declared Emma to be the “Saviour”, and if his knowledge of the purpose of the Curse only went so far as his own involvement in it – so acquiring it, setting up the situation where it was cast, and seeing to it that it could be broken to he could find his son – then yeah, she was the Saviour as far as he knew.
But if the Curse was really just part of a larger game, which Pan is aware of, then from Pan’s perspective, the objective, and therefore the “Saviour” is different.