I'm pretty sure that when the AuthentiSEAL database was in business they indicated that he really had been a SEAL.
The closest he can come to saying he was a SEAL is to say, "SEALs and UDT were the same." and that's another big fat lie. SEALs were running combat patrols in VN, while UDTs were doing lead line platoon floats on ARGs, preparing for the next WW2-style beach invasion that never came.
Here's the best article exposing Jesse The Liar. It lays it out in exact detail.