Mine's got it. It poses no problems so far as I'm concerned. All my 3rd GEN pistols have this feature. Probably not a bad idea on a pistol of this type....
S&W would do what ever the customer wanted. Some have the magazine disconnect, some don't, it was a special option like night sights. I have one 1076 with the disconnect and one without. Agency's choice.
To the best of my knowledge, any 3rd Generation pistol that left the factory without the magazine disconnect will have an imprint on the slide that reads Caution: Fires without magazine, or something similar.