I think that Flaming Gorge is a hydroelectric project and, like Glen Canyon Dam, releases to meet the daily electricity demand fluctuations.
My understanding is the flow on the Ark is released at a constant rate because the fluctuations in discharge take a couple of days to get from the dam to Canon City. They just can't time the flows for maximum daytime recreation for the whole AHRA section.
Nothing in the world is more yielding and gentle than water. Yet it has no equal for conquering the resistant and tough. The flexible can overcome the unbending; the soft can overcome the hard. - Lao Tse