You clearly didn't understand my post. To be clear, you should NEVER operate the slide stop lever to release the slide from its locked-open position. There are still instructors out there that teach that, but many do not anymore. Every time you want to release the slide from its locked-open position, rack it. There is no need to fiddle around with the slide stop lever. There is also no need for learning two different procedures for the same action. The main reason why instructors have moved to this is to simplify the operation of a firearm. Some instructors may argue that this is a gross vs. fine motor skills issue, but for me this is a pure "consistency so it works under stress" issue. Have you ever given the thought that you may need to operate your "right-handed" handgun with your left hand, such as when you are injured? You would run into the same issue as a righty. Watch this instructional video to understand what I mean:
James Yeager | How to Reload Your Pistol and Rifle - Part 1 of 3
I consider the S&W M&P Shield 9mm ambidextrous as long as it does not have a safety or you don't use the safety.
PS: Note that the slide stop is sometimes referred to as the slide lock, which adds more confusion. On a Glock, the slide stop keeps the slide locked open when the magazine is empty, while the slide lock is operated to disassemble the firearm.