I think that is true. The thing is that would mean that Tremaine is his daughter because they are really hinting that Tremaine is Rapunzel.
I do agree that the writers may hint at things though that nothing comes of. This happens all the time because these writers are very bad writers. They may hint that Tremaine and Alice are Rapunzel and Hook’s daughter, and then turn around and make random person number one be either of those people. These writers think that trick writing is better then building a narrative, which they are very wrong about and that is one of the biggest reasons their show is just not that interesting anymore.
We are all here discussing the hints in the show and trying to figure out the mystery and it should be possible to do so. The hints should actually mean something, but since these writers are absolutely terrible, they might not mean a thing, and if that is so, again, then there will be no point in discussing the hints because they are meaningless.
We will see. The writers said they were going to write mystery again. We will see if they actually do or if they just continue to write very bad and pointless trick writing.