My guess is that because the nozzle is adjustable, Rain Bird wanted the flange easier to grip so you could pull the stem up and adjust it with the water off if you need to set it to a pattern that would get you wet if the water was on.
Anyway, I did modify one of my 1800 sprayheads to lower the nozzle by grinding the little tabs off at the very bottom of the stem where it sits in the casing. The tabs are there to raise the stem a bit to allow the water to get under and into the stem if you are using the side feed on the sprayhead. As long as you feed the sprayhead from the bottom grinding off the tabs won't affect operation but will lower the nozzle almost 1/8". I will monitor this sprayhead and see how it works and consider doing the same to the other sprayheads if their nozzles tend to get clogged with sand.
I should add that this is the first time I have removed the nozzles in eight years and none of the filter screens had debris, so leaving out the filter screen to lower a VAN nozzle is also probably worth trying.
My sprinklers run overnight, so I almost never see them in operation and only check them if I notice a problem with the grass. That being the case, I like a set-and-forget solution.