This would probably have a response in the ask a cuemaker forum, or do a search there and there's probably a video somewhere. There's lots of good full-splice cuemakers. My favorite is a John Davis full-splice blank finished into a cue by a cuemaker known for building playablility, that has developed the tapers for a really fine, highly playable cue. I love the full splice hit, and there's quite a few cuemakers that appreciate the quality of a John Davis blank to enjoy the opportunity to put their own personal mojo into a full splice cue. Mark Bear just died this year, he was also very well known for building a really fine full splice blank that was used by many. RIP Mark.
Sorry I don't have the technical knowledge to answer your CNC question, but I'm pretty sure that the ones built by John Davis and Mark Bear were done by hand.