Tromba—
Your slide lock is obviously also a release and was designed that way. If it could not release the slide, the slide would always stay locked back, right?
Now, HOW it releases the locked slide leads to controversy, but as with so many issues dealing with handling firearms, there is more than one way to deactivate the lock. It comes down to personal preference for most pistols.
S&W takes the easy, cheap way of manufacturing their Shield slide locks. They make no extra effort to provide the simple friction-oriented geometry and finish work that allows the slide lock to be released with finger pressure or even “automatically” when a loaded magazine is inserted briskly.
From the factory, most Shields have too much friction between the slide lock lever and the corresponding locking notch in the slide. Only by retracting the slide to relieve that friction and allow the slide stop return spring to force the lever down can you close the slide. The manual does instruct this one method that generally requires two hands to accomplish, is slow for speed purposes, and which is not fool proof.
There is slingshotting which is pinching the rear of the slide between your thumb and the knuckle of a finger—like a slingshot. This is arguably very difficult to do on a sub-compact pistol with strong recoil springs, especially when new. Some people cannot physically accomplish this supposedly preferred method. It is a very weak method ill-suited to running a Shield carried for personal defense.
There are also variations of the “overhand” method that work better and are now the preferred method. Some folks mistakenly refer to this as the slingshot method also.
However, a simple adjustment of the friction between the slide lock lever and the slide locking notch allows both these methods to be used, OR you can use a finger to deactivate the slide stop—thus allowing you (Oh Heavens!) to refer to it as a release also, as some more advanced manufacturers do.
As mentioned, there is plenty of prior discussion on this forum, and plenty of complaints about stiff slide stops, even on YouTube. If you like your gun except for this manufacturing laziness, simply fix it. You can run your gun any way you want. Many competitors and combat instructors do favor using the lever as a release because it is faster and may make one handed manipulation easier.
I have adjusted the slide stops on over a dozen pistols to release easily with finger pressure. My carry pieces all will close with the “auto-forward” feature backed up by finger pressure. It’s just mechanics. Do what you want.
Welcome to the forum.