I don't think I've ever had this issue with my gen 5 - but I'm also not sure if I've tried to drop an open slide with an empty magazine inserted. Will attempt and report back tonight.
As for the rack vs. slide stop argument, I've asked multiple instructors which method to use and why and the consensus seems to be exactly what Lugar223 quoted - IT DOESN'T MATTER. One instructor told me that the slide stop was preferred by most militaries and manufacturers up until the '40s, when Israel was created and their military was established - because they were using a multitude of different sidearms from different origins at that point, they decided to train soldiers to rack the slide to avoid nuances and differences between different pistols' slide stops. To me, this doesn't mean that using either method is incorrect, but it may depend on the firearm - and racking the slide may be a safer bet if you're deciding between one or the other.
The story above may be incorrect, as I'm going off of what "a guy" once told me, but now that that horse is beaten past dead...
I rented a Range to El Al Security for 16 years, so I can tell you for sure, that is where the carrying chamber empty came from, so many different pistols they, the Isralies "Acquired" sure way of finding that first, and subsequent shots. Rack and fire was the way to go. Now they have gone to Glocks, one up the spout is the name of the game.
Not sure if I have mentioned this here or not?
But when they changed to Glock 17s, the El Al flight that brought the Glock pistols, took the Hi Powers away.
But no Glock magazines were supplied! Because the powers that be in the Israeli Consulate decided to conform to Canadian magazine law, 10 rounds! So the 17 round ones, stayed at home!
Knowing my relationship with Glock GA, they had already been told, by phone, it will take a month!!
Spoke to the boss, in Smyrna. "You cannot jump numbers on the ordering dates, first come first served!"
I explained the dire need. The 10 round magazines were sent, received next day! They were a gift? A cheque was sent, to the Glock Sports Foundation? A donation. Fixed.
The original Browning's still had the magazine cut out in them, would not fire with no mag in place.
The reason they came to me, for renting a range, when the Police Ranges were free? The Cops were watching their range drills! So was I, but what I saw, stayed.
One in particular (this info is over 20 years old!) On command, draw and fire, three rounds at 15 yards, at an SAS Canada Target, run forward, use a funny flat foot halt, and shoot a 4" ballon, taped to the concrete, under the target! Lots of close quarters movement with guns in hand! Not the Gun Club method. They had no ability to carry outside of the Consulate, or Terminal 3. So guns came in bags, in trunks.
Ammo black tip Sub Gun, mil-spec hardball, in 32 round Israeli boxes Which were burnt in the stove prior to Tim Horton lunch! Great Chili. Definitely, guys, you would want on your side in a gunfight!