Jerry, you may not read this, but as 36sedan says your rule of thumb may be right for tapped holes in plate or blind holes, but you're overlooking that the first step in that process is that the bolt is sized or selected for the tensile strength needed to withstand breaking. Step one, what size bolt is required; step two, calculate the depth of thread that's needed to restrain the bolt such that the bolt shears at or above the first exposed thread. That second calc deals with tensile stress area of the threads, the bolt major diameter, and the thread pitch.
In this application I picked 1/4" stainless bolts to fit the hole in the latch bracket, but more for appearance. There are two per latch, and that is very definitely over kill on strength for the application. Rather than consider the application and number of bolts per latch you simply jumped in criticizing the approach, preaching that what I had done is wrong. I agree that a couple of SS acorn nuts on the bottom of the back latch bolts is a nice finishing touch to cover the exposed threads, but I do not believe that nuts are needed on either place, for this application.
When you choose to pass on your wisdom it's probably best to focus on the specific task being discussed, or if a "general rule of thumb" is what you choose then explain the basis for that rule, and that it may or may not apply in this case. Just my humble opinion, and you can take it or leave it.