Not trying to create an argument, but your mass smite would still be invalid. If the warden declared a freeday that was determined to be an invalid order by staff on, you would just say in allchat/mic that since the warden gave an invalid order, that the remainder of the day would be an invalid freeday, due to the warden's mistake. If a warden was to give some other kind of order that was determined to be invalid by staff (ex: "standing is restricted, all T's please shift-walk follow me), you would just say that the warden tarped, and not smite @all or something like that. Even if the warden screwed up to the point of giving an invalid warday area, you wouldn't just smite @all, you would declare the day an invalid freeday.
Regarding the ability to smite/slay @all on Late-Nite Jailbreak, the situations are much different as Hidingmaster said. As long as it's done with approval of other staff/not overdone/not interfering with the ability to play Jailbreak, I think it's fine, considering that this is supposed to be much more laid-off than a normal day of Jailbreak.