Well, Future Guy must be lying because he always is.
Although what he said or did never made any sense anyway. He never stayed consistently on anybody's side, and his helping or hindering Archer balanced out rather exactly... But perhaps he was simply a pathological liar?
What's funny about that is according to Brannon Braga, if there had been a season 5 of Enterprise, Future Guy was going to be revealed as Archer himself.
Of course, he may have been joking but it would have been interesting to see how that played out.
Archer being Future Guy would make about as much sense as a WWE wrestling story line.