I think at this point S&W is just trying to keep in the game and take some market share from Ruger and Taurus. Their Semi autos don't have the lock except as an option. But just to show you may be right... look how long it took for S&W to catch up on the whole AR game.
Good point garand, another would be the M+P, the knee jerk reaction to the Glock by S&W was the Sigma, marginal at best when they first came out, and now a decent pistol, (still for right handers), BUT they got it right on the M+P line.
The S&W AR's are based on the the exact spec of the STAG line, and function as such. Good ammo + maint. they go bang every time.
Not sure if it was "catching up" , or just trying to get it right in the market. References could be made about a certain Ruger SR9 that was "rushed" to market only to realize it wasn't quite "there" yet....