Over dwelling the valve creates more noise.
While valid adjusting ... the conversation of dwell & noise is a completely different discussion.
You can do these types of "what ifs" until the cows come home....Bob
You can also change dwell by changing the valve closing force, valve spring and valve stem diameter in traditional poppet valves.
You can learn a bit about muzzle pressure from this article....https://hardairmagazine.com/ham-columns/how-to-obtain-the-maximum-power-from-a-pcp-air-rifle/and here....https://hardairmagazine.com/ham-columns/pcp-airgun-internal-ballistics/Bob
I often find that you only lose about 4-5% in velocity when the valve closes at the midpoint of the barrel.... You are only using half the air, so the total mass to be accelerated is considerably less, meaning that more of the total energy ends up in the projectile.... That 88% FPE is probably conservative.... and a LOT quieter....Bob