It IS covered by the rules. The rules say it will start on the ready, as there was no major clock stopper to end the previous play. You don't get to make up new rules just to be "fair". If that were the case, we wouldn't have the debacle of a defensive holding call that causes a sack to be marked off from the end of the run, we wouldn't have a lock of first down on DPI, and a plethora of other rule loopholes.
"Coach, have your team ready, the clock will start on the ready whistle."