Jacob
What goes around comes around.
If you simply hold it at the same angle every time you hone or grind, this also "maintains" the bevel. More reliably than relying on a hollow - it's difficult to be sure that your hollow will sit exactly within the chosen angle.....
For me, the advantage of honing on the hollow is that the bevel angle is maintained. ....
If you want to hone an edge at 30º just hold it at 30º.
Hmm, maybe a diagram would help?