I heard a theory (from 3424896o6 they came up with it, check out their book for a better description of their theory!)
saying that Tam could be faking being nice and he really is working for the Neverseen, as much as I don't want this to happen there is some evidence:in legacy they all question Tams loyalty while he's with the Neverseen, mr forkle says
Sophie even says she's worried the shadowflux might influence his actions and the flux could change him. Then he's getting all close to Glimmer and we still don't know if she's good or bad, either the two of them really do like each other or they are plotting against the Black Swan