I don't think he was as wide open as you think, a few times Gonzalez tried and Gamboa even though he was coming in, still got out of the way.

I don't think Meldrick Taylor IMO was p4p faster than Roy JOnes Jr or the like, but his speed and punches seemed effortless, and Gamboa throws his punches with that same ease. Calzaghe also throws punches like them. You don't hear a hiss, they aren't expending all their energy, they just punching naturally, only M. Taylor and Gamboa to a greater extent do it at lightning speeds. I think Gamboa also has much faster feet and better footwork than Taylor when he uses it.