I have talked before about two things that I do not believe people train enough on. One is your draw and the second is reloading. Here is one challenge that I challenge you to do. How fast can you reload? Seven mags with one round in each for a total of seven rounds, how fast can you reload?
Notice how she never once used the slide lock to drop the slide forward each time. 
You know that slide lock reload practice for self defence is useless… 
Yeah.. it is sexy… and it’s a good to know how efficiently do this, just in case… But super speed is not needed for it .
Yeah, seven mags is.
I know a guy that has survived a lot of combat. His support hand goes straight up to grip position while simultaneously releasing the slide lock - no wasted motion. He is the quickest reload I’ve ever seen.
Lena has been trained by the best. What is the rational for the wasted motion grabbing the slide to release? I am not criticizing, she would be through all 7 while I am on #2
Do you mean he releases the mag before he fires the round?
Watching Lena do these “SPEED” challenges kinda reminds me of the Mitchell Labor Guide I use at work to calculate labor times on vehicle repairs. She has all her tools and parts laid out on the table and is shooting in perfect conditions.
Mitchell does the same thing, using Master Technicians who are working in perfect conditions with all their tools and parts laid out on a table in order of how they will be used during the job.
If a particular job calls for 3.5 hours by the Mitchell Labor Guide, we always add approximately 35% to their 3.5 hours which would come out to 4.725 hours of labor on the invoice to the customer.
Using that ratio, Lena’s 15.11 would come out to 20.39. I would call that acceptable.
He releases the empty magazine that has locked the slide back. He inserts a new loaded magazine with his support hand. He then moves his support hand into grip position while simultaneously releasing the slide lock.
I couldn’t see your hands very well, but that’s what it looked like to me she was doing it just took a while for the slide to fall.
I do the same thing with my Beretta. The “9” series pistols (M9, 92, 96, 90two, 92A1, …) all have a big chunky slide release directly above where the strong hand thumb would be for a right-handed shooter. I practice my reloads pretty much the same as Gary_H describes without ever taking my eyes off the target area and my spare mags come out of mag carriers on my belt or vest, not lined up and spaced on a table.
Watching Lena go through her drill, she knows she is on a range and the targets aren’t shooting back or diving for cover. She constantly looks down at the table for the next magazine and always looks at her weapon to ensure she is loading the new mag correctly.
I would have chambered the first round dropped the mag and loaded second mag fired the shot dropped the mag and loaded the third mag… That probably would have been cheating.
I like that thinking, to make it easier is smarter. Keep it simple.
So she doesn’t break her grip, the thumb to drop the slide will stay in place.
Hth
In my thinking, I rack the slide with magazine changes for one overarching reason: it is part of the same thing I’m going to do to clear a malfunction.
Different places I’ve trained suggest different things on the reload.
Masad Ayoob–shows the retired military guy who uses slide release to get the fastest reload time.
Tactical Defense Institute–rack the slide.
Rob Pincus–rack the slide.
Masad Ayoob recommends using the Israeli technique for racking the slide when doing an administrative reload. Rather than your thumb facing back towards you when racking the slide, your thumb faces forward on the dominant side of the slide to give you greater contact with the slide.
I will say it was nice to see Lena “miss” the mag well on a mag or two. Now I don’t feel so bad when I do it. 
I need to practice reloads more often. I’d love to see her do this drill while not standing still on the reload.
I don’t understand. Her right hand would never break grip if she released the slide release with her left hand.
The left hand has to break grip to load the magazine, but hitting the slide release on the way to full support grip is a shorter path than reaching over the top of the pistol to release the slide.
Maybe I’m not communicating well?
I think you are communicating well I just couldn’t see which thumb she was using to release the slide. She wouldn’t be reaching over a gun to release the slide. She would be releasing it with her right hand thumb, which is on that side anyway.
The point is she is not using the slide release at all.
She pulls the slide back and “sling-shots” it into battery.
Oh yeah now I see it. Maybe it is easier than reaching the slide release. Maybe she is doing it in case the slide doesn’t lock back.
I wonder how many times while working on this she accidentally released the slide before the magazine was seated???
As @BruceE noted, a full size handgun like the 92FS has an easy to operate slide release. I rack the slide on my P365 because the release is small and stiff. It depends on a gun’s particular ergonomics. Everything is stiff on that little gun, especially for me as I have arthritis in my hands. I’ve replaced both the trigger and slide springs with softer ones for that reason. Besides, the gooberment trained me to rack the slide.
That’s my story and I’m sticking to it.