Praetorian Foil is a rare gun. Gjallarhorn is far from a rare gun. The thing is, it's coveted. Not having one is much worse than not having a No Land Beyond - so the absence is noted more. That is a psychological effect, not a statistical one. With any low chance drop rate - there are those that are going to be blessed with getting it early for no reason, and there are those that are going to be screwed over for a long time - equally with no reason. That is a statistical effect.