I've looked at it with a banjo neck. Results were actually better doing one-sided (fretboard side down), or two sided (left side, right side) machining on the table rather than rotary. With the longer heel of an acoustic guitar neck I'd use the left-side, right-side approach. Doing them on the table means you can make a number of them at once.
Gary Beckwith uses a similar technique making sets of table legs.
I just set up a 2 rail sweep to match the width of the 8 leg blanks.(plus a minor over run)
Set blocks on the table to push the blanks against for registration
Clamped the blanks together and ran machine relief in raster across the 8 blanks. I also clamped dunage (scrap 1x4) on the sides to control chip out
Rotated each blank 90° re-clamped and re-ran the toolpath, repeated for all sides
You will see I left an inch or so on the end to keep the blanks in the horizontal plane, which were removed at the mitre saw later
This is a more efficient way to cut tapered legs than using the indexer