My personal guess would be that the no show fee is part of their standard conditions, which they typically retain on paid bookings unless you try to change them (or even the two night bookings) but in all likelihood do not claim on the free 24 hour stopover (though of course, they might also send you an email asking you to pay). Note that this would be in line with no shows on airlines - many tickets (not least on QR) have no show fees, but typically, those are only levied (in addition to change fees) when you try to refund or change your ticket, not when you just do not show up and forfeit your ticket entirely.