Countdown Tiles counting off two turns instead of one

I finally observed what some people have been suspecting. Countdown tiles can count off twice in one turn. It happens like this:

1. Tile A goes from 2 to 1.
2. Tile B goes from 1 to 0, activating.
3. The cascade from Tile B's activation causes Tile A to drop to lower position on the board than Tile B was.
4. Tile A counts down again, from 1 to 0, activating.


This all happens at the beginning of a single AI turn. Tile A could have any number on it, but the fact is that it can count down twice in one turn.