The waiver applies to visitors who book two consecutive nights in Jordan before entering the site, and it is claimed at the gate rather than in advance. Day-trippers arriving from Israel or from a cruise call at Aqaba pay the full rate, which is the point of the policy.
For students already in the region on a program, the arithmetic is straightforward: two nights in a Wadi Musa hostel costs less than the single-day admission it replaces. Bring the booking confirmation on paper. Staff have been inconsistent about accepting a phone screen.