Alternative take:
I'm sure Warmoths requirement to finish a maple neck is a good insurance policy for the company, and prevents them from paying for a lot of things that are the user's fault, but it seems to me that whether a maple neck will warp or not (how affected by moisture, basically) will depend on: neck thickness, neck construction type, density of that particular piece of maple, local humidity and seasonal variation, and amount of use / hand sweat the neck gets. Warmoth isn't saying your maple neck WILL warp, they're just saying that it might and it's not their fault if it does.
I've been playing an unfinished maple neck for a year with no need to adjust the truss rod at all. I know that's not very long so take it for what it's worth. It's also: A clapton back (thicker than normal), warmoth pro (double truss rod for stability), a very dense piece of wood noticeably heavier than my other maple neck, and I live in a dry climate with not much seasonal change (lala land). The tech I talked to, who runs the shop at TrueTone music, possibly the best guitar store in LA, said that it wasn't that big a deal to have an unfinished maple neck, it 'might need a bit more frequent truss rod adjustments'. It's really wonderful to play on.
I also just finished my new maple neck (a strat neck) with Deft semi-gloss spray lacquer, and while it's not as smooth as naked neck, it's a lot smoother than some of the high-gloss necks you'll find. It was WAY easier than tung-oiling and took only a couple hours for four light coats (just one $5 can), and then 10 days to dry, and a nice thorough buffing with super fine steel wool. It looks very professional and I'd recommend it as a finishing method for a beginner. I was scared of spraying, as I've never sprayed anything that didn't run, but I just followed directions, went slow, and it turned out great.
Alternatively, everyone here says Canary necks are awesome substitutes for maple and feel great, so if you've got the $$, why not?