The problem with machining a taper like that is you get many spiral ridges in the surface which need to be polished out. That polishing trashes your tolerances making it low and/or out of round in some spots. Which then makes it harder to remove thank if it wasn't tapered in the first place. Now granted, this was explained to me 15+ years ago, things may have changed since then, and your polishing may be more precise than mine. Or your budget may be way higher.
Well I added those photos but deleted the associated text and the photos. Not sure why they still show up.