Smith & Wesson was purchased by a AZ based corporation in the early 2000s.
The new owners/mgmt changed a few designs and to reduce civil lawsuits/make elected officials & police chiefs happy, started to add security locks.
Author & tactics trainer Massad Ayoob put out a few gun press items in the 2000s about how the Sc & N frame type Smith and Wesson magnums would break or malfunction.
Ayoob(a reserve/sworn LE captain) told the story of a police investigator who purchased a S&W security lock 329 .44magnum to replace a model 629 Backpacker he'd carry on duty. The cop's new .44magnum misfired several times. He went back to carrying the older S&W N frame Backpacker snub.