On any flavor of race bike that isn't used on a Velodrome fast reliable wheel changes can make the difference between DFL, DNF or a more respectable finish.
Vertical rear dropouts are the easiest, quickest and most unlikely to bodge a rear wheel change on, particularly under the pressure of an in-race wheel change.
Many of us warm up on the "B" wheels and install the race wheels before the start. Screwing that up is about the last thing up need when your class is being called to line up.
Reliable and light In That Order make for a good 'Cross bike in any racing class. Put a tensioner on vertical dropouts and have at it.

-Bandera