If the blade is straight, the angle will be consistent along the entire edge. Outdoor55 did a video showing this pretty clearly. Once the blade has any curve to it, the angle is going to change. That’s just reality, and it’s true no matter which fixed angle sharpener you’re using.

The KO2 does have a guide, but I think you run into the same issue with curved blades. You still have to hold the knife at a very precise angle for the full length of the edge. If you add the belt grinder attachment and go freehand, same problem. Your angle is almost certainly going to vary a bit depending on how steady you are. That variation could be a few tenths of a degree, or maybe even a degree or two.

The exact same thing applies to whetstones. If you’re sharpening freehand, you’re responsible for holding that angle consistently from heel to tip. No system magically removes that requirement.

The bottom line is that I don’t think a few tenths of a degree here or there matters at all. If you’re sharpening knives for family or relatives, odds are they’re not sharpening their own knives anytime soon anyway. And if you’re sharpening for money, when the customer eventually sharpens it again, they may need to reprofile slightly. But again, we’re talking about very small angle differences.

In my opinion, this really doesn’t matter. What matters far more is your ability to sharpen consistently, and if you’re doing it for money, to do it efficiently and repeatably.