The gentleman is correct to mention purple Loctite. Screws below 1/4 in in diameter should use purple or equivalent. I think many get by with blue by not using it correctly in the first place. A clean small screw and thread treated with blue can be a bear to remove.
There is a tolerance on screws and threads, so you can run across installations which resist backing out or not under vibration. Loctite is the proper way to prevent problems with screwed connections. Lock washers remove metal whenever disassembled and are not as desireable.
If S&W has a design problem, then so does any screwed assembly in industry. A customers lack of knowledge of screwed assemblies is not their problem.
Torque is to maintain proper clamping pressure, not to prevent loosening of a joint. Proper torque prevents damage to a screwed assembly.