IMHO, yes, the startle response and fear are two very different animals. The startle response is a reaction to an external stimuli. A fear response is a reaction to a negative internal fantasy. I am not saying that the fear isn't accurate in its possibility. While I see the need for more realistic training so it generalizes to the outside world better, I do not see the need for it to be fear based.
Einstein said that the type of thinking that creates a problem is never the type of thinking that solves it. Fight, flight, and freeze are all fear based. Flow is not.