While true, the penalty has to be deemed to have been a clock preservation play -- not necessarily that that was the intention but it needs to be the result. If the official judges that it was not a stop the clock play, there is no 10 second run off and the clock is rewound when the U signals the ball ready for play.
For example, an illegal shift penalty (or any other formation penalty that does not stop the clock but instead allows the play to be run) will virtually never result in a 10 second run off. (Happened this weekend in fact.) Really, the only offensive penalty that actually halts play immediately is a false start, so that's the only situation where you will see a 10 second run off, for all practical purposes. Occasionally you can have a run off on an unsportsmanlike conduct penaly since that also causes an immediate whistle and clock stoppage.
