Taste, especially sweetness, is very subjective. Most flavors have sweetness of one form or another if the flavor would have a sweetness to it that the concentrate would need to convey to make it seem right. There are some specific flavors that don't have a sweetness to them, that if you'd want it to be sweet, you'd add sweetness, or, as I see it, in certain cases, flavors like cotton candy, that aren't exactly sweet, but are close to it, with a note that the brain associates with sweet. This is more common the more complex the recipe, as sweetness can blend flavors together
Then there are companies like medicine flower, and river supply terpene line, that are terpenes only. These areabout 40 or so natural chemicals that have distinct aromas. These can be blended together in specific ratios to create a wide range of flavors, but have no sweetness added, yet can still mimic things like fruity boulders or thin mints...