Only one problem with the someone else saving a piece of EF/FTL theory – Rumple, Jefferson & Regina all knew with 100% certainty that EF/FTL still existed post curse- while the curse was active & after it had being broken.
I think that Rumple & Regina knew it did on account of them being involved with bringing the curse to bear & Jefferson knew because his Hat connected to EF when Regina wanted to get magic (unless he knew more about Regina/Rumple’s curse than we know).