I’m sensing proofreading isn’t super high on the list when they send the rules out…
9.3.9.1. The Toyo RR or RA-1, size 205/50/15 must be used in qualifying and competition. Any tire brand/size may be used in practice or other non-competition sessions
9.3.9.5. Wheels shall be 14 by 6 inches, 14 by 6.5 inches, or 15 by 7 inches, and shall weigh a minimum of thirteen (13) pounds. Any brand, unless specified in these regulations, is allowed.
Now, I suppose you could use a 14" tire for practice, but why?