Tales and Chronicles
Jewel of the North, formerly know as vincegetorix
Well, to be fair, I dont even have to put this kind of anti-cheese clause in my houserule at my table. I guess my players understood the idea and intention behind the switch and do not try to cheese it.Smite Spells all take bonus actions. So it's definitely not something that could be meaningfully done in combat.
I bet he also has some restrictions on using more than 1 at a time to prevent the precasting more than 1 scenario you are envisioning. Probably just didn't seem worth elaborating to that level of detail.
anyway, as you say, it requires a bonus action to cast a smite spell and, out of combat, I use 10-minutes rounds, to by the time a player gets another turn, the pre-cast smite is pretty ended. So in combat I guess a player could wait multiple turn to cast a bunch of smite spells to prepare a super-hit, but I really doubt my players would even think of this kinda things.