Yes, but people would reason to look under the door to see if someone is in there.
What a real gunner needs to do, is scope out how many stalls there are before the exam and bring the appropriate number of pairs of shoes with pants. This, of course, would be much more difficult if the spacing under the door is any more than 6"-8" as not seeing legs would become an issue. This way, when someone looked, it would appear that someone really is on the pot and they would either have to pee into the sinks or find a bush outside, both of which would be tremendously time consuming because most people would request that everyone leave the bathroom so that can "use the sink."
This is fun...