Like someone else said "I make it a habit to check the chamber before I use a gun ,first, anyway" with that said , I can really only see one possible use for this , if you need a gun in a hurry and your the kinda guy who leaves guns around the house unloaded ,or with a mag in , but havent pulled the slide back yet !
But who would do that? The reason that gun is on the nightstand (preferably under the nightstand ) is so you can grab it and shoot right? Nope theres no use or excuse for the little notch in the slide!
Why not leave the gun on the night stand? Well if your sound sleeper and you live in the city /suburbs you might have left your door unlocked , when the perp walks in ,pets your dogs head , he walks into your room while your sleeping , walks over to your nightstand "Wow a Glock 23" , "mine" and before you wake up and startle him you'll be shot dead , or he'll leave and kill a store clerk in a robbery with your gun ! HIDE IT! Under the nightstand , I like the holster that sleeves the mattress !