The "optimal" cut quality top and bottom from a compression tool actually does have a bit of the tip into the spoilboard (which is why it's called a spoilboard) as it provides a better "uplift" to avoid tearout on the bottom. That's practical for big machines in production because they typically use vacuum on sheet stock and frequently replace the spoilboard. It's less practical for those of us who are either hobbyists or small operators because the economics are not there for frequent spoilboard changes or milling off so "kissing" the spoilboard has to be good enough. For many materials, that's just fine and the bottom surface should be reasonably good.
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The most expensive tool is the one you buy "cheaply" and often...