To FF: You are correct. I use a Jabsco Sensor-Max VSD water pump. It does not require an accumulator to operate. And yes, the pump turns on and all fresh water passes through it whenever a downstream tap is opened, even ever so slightly. It's a real good leak detector, as any cycling of the pump without a fixture being opened is a sure sign of a leak in the fresh water system somewhere.
To Larry M: I have had a difficult time in the past researching factual, honest, low level scientific- or engineering-level information from most vendors of marine products. Starting at the vendor level, they are typically sales persons, with little or no technical knowledge of their products. Pushing past them to the actual manufacturers of the product is difficult, as many marine products are foreign-made. So....often I've had to rely on some intuition (backed by 43+ years in related technical fields) to refine my boat's system designs.
Regarding warm up of the light used in a UV sterilizer, yours is a fine example. As you point out, various vendors provide varying information. For instance, what is "full germicidal output"? How much "output" is provided by the bulb upon instantaneous startup? 1/2? 1/10? How much is enough? Is the type and/or manufacturer of the bulb the same as mine? Who knows? Aaarrrrhhh, makes my teeth hurt!
So, I make best estimates, based on information at hand, and go forward. Should my solution differ from your preference, so be it. A simple fix is to remove the pressure switch, and operate the UV sterilizer 24/7. With a bulb service life in my case of 9000 hours, my guess is no harm, no foul. I certainly DO NOT claim to have all the answers, but simply proceed with what works for me.