Did I hear this as correct? ...you insert a new mag and... the slide release automatically releases and a round is chambered.
Yes, you heard that correctly. It's typically referred to as
auto-forward.
The way you described it -- "When the new mag locks..." sort of suggests there's a mechanism designed to cause this. That's not quite what's happening. Here's how the slide stop is supposed to work:
If you will look at one of your magazines empty, you will see a notch in the front left "nose" of the follower. That notch lines up with the slide release. That notch allows the follower to get high enough that the last bullet in the mag is high enough to get caught be the slide and driven forward into the chamber without the follower pushing up on the slide stop. Once the last bullet is out of the mag, the next time the pistol is fired, the follower will be high enough to push up the slide stop, and that is what locks the slide back.
Now, with pistols that will auto forward, the loaded magazine is interacting with the slide stop with a little bit of violence and knocking it out of engagement. It typically requires significant force to produce the effect. My CZ P-09 and HK VP9 do it easily enough that driving the mag home deliberately and firmly with moderate force will auto-forward the slide every time. All the other semi-automatic pistols I own, including a CZ-75 Shadow Line, require me to really slam the mag home harder than what I am comfortable doing. When I use the VP9 (current competition gun) in competition under the clock, I auto-forward every reload from slide lock. When I have used the 75 Shadow Line in competition (it's been a while), I rack the slide manually.
Just because you see a reviewer say the P-10 does this doesn't mean it's a designed feature, nor does it mean that all samples will auto-forward easily. I haven't seen CZ promote it as a feature (which doesn't mean they haven't), and unless I see CZ promoting it, I won't assume my samples of the P-10 will auto-forward easily until I get them in hand and check them. I hope they do, but I won't complain they're not working right if they don't.
