I'm Not Sure This is Correct...Is It?

[OverAndBack]

From a quiz in an officiating magazine:

Team A, trailing by five points and out of timeouts, has the ball first and goal on Team B's nine yard line. A2 catches a pass and is tackled inbounds on team B's one yard line. During the down A2 was flagged for pass interference and the penalty is accepted.
a. The penalty is 10 yards.
b. The penalty is 15 yards and a loss of down.
c. The penalty is 15 yards.
d. The clock starts on the snap.
e. The clock starts on the ready.
f. If the clock expires before team A can snap the ball, the period is extended for an untimed down.
g. If the clock expires before team A can snap the ball, the game is over.

The magazine lists the answers as b, e and f. I know it's fifteen yards and loss of down for OPI (7-5-10a Pen). Clock starts on the ready, fine. But I'm confused about (f) as it pertains to NFHS:

3-3-3: A period must be extended by an untimed down if during the last timed down of the period, one of the following occured: (a) There was a foul by either team and the penalty is accepted, except for those fouls listed in 3-3-4b.

3-3-4: A period shall not be extended by an untimed down if during the last timed down of the period, one of the following occurs:
(b) There was a foul by either team and the penalty is accepted for:
1. unsportsmanlike fouls,
2. non-player fouls,
3.fouls that specify a loss of down

As OPI specifies a loss of down, you wouldn't extend the period for an untimed down, would you?

I know this is esoteric, but I wanted to be sure I wasn't reading something into this that isn't there or missing something.