Fridge Logic: Loads. If Thomas Veil never existed in the first place and, his identity was created by the Conspiracy out of whole cloth, what does that say about the other erased people Tom met? At one point Tom met a town full of erased people and a man who was erased by the Conspiracy over twenty years ago. Are we to infer that these people were also brainwashed to believe they were someone they weren't? There is also the episode "Father" where Tom meets his estranged father (whom he hadn't seen in twenty years). The episode strongly implies that the man really is his father and not just another Conspiracy plot. Was this just more mind games by the Conspiracy?
It's possible that the Conspiracy had erased people in the past, just not John Vale.
Thom's dad (and thoms name) was likely real though. everything else wasn't...maybe