Night of the Striga

Quick-Play
Activate only when an opponent's monster is changed to Defense Position. Send it to the Graveyard and Draw 1 Card.

Quick-Play
Activate only when an opponent's monster(s) is changed to Defense Position. Send one of them to the Graveyard and Draw 1 Card.

looks good to me

But but

now when you shift all their monsters to Defense with a different card you can't flip that and kill them all.

thank goodness XD

well, this was to clear up rulings. If you used that effect, someone could either interpret it like you did or think "more than 1 was changed, and this doesn't say anything about multiple targets, so I can't use it"