It's all a matter of degree. I've never seen a Warmoth neck that wasn't playable right out of the box, and I've seen a lot of them. Hell, it wouldn't take long shipping unplayable necks before they wouldn't be asked to ship any more necks, no matter how low the price or how pretty the wood was.
But, it's a simple matter of fact that they are built to allow for fine-tuning to suit a particular setup/playing style. The frets aren't dressed because not everybody wants them dressed, or dressed the same way. The nuts are cut well, but shallow to allow for different gauge string sets or playing styles to be implemented. The frets are as level as they can be, considering they're mounted in wood, but there's going to be some variation because of that. Usually, it's too little to matter for most, but for those who want low action or who have a light touch, it's worth going through them and making sure they're perfect.
It's no hit on Warmoth - they even mention on their commercial site that for best performance a professional setup should be performed. Most new necks are built that way, regardless of manufacturer, for the same reasons.