"It sounds like you either disagree that this could happen or disagree that if it happened it would affect the trigger work."
My interest in 1911's is in scoring well with them, not their internals. But I have been around quite a few tuned 1911's, and haven't heard of any problems from keeping your finger off the trigger when dropping the slide. My sense is that either it's an old wife's tale, or it only applied to some very old trigger jobs. My match 1911 was old when I bought it, for example. I was the third long term owner (there are local shooters who can give you the genealogy of most of the guns on the line), and I bought it 20 years ago
, so I think you'd need a very old, or poorly done, trigger to have problems.
My advice would be to drop the slide with abandon, and if your trigger goes south, get it repaired to modern standards.
While we're discussing 1911 kinks: I know lots of people who drop their hammers on an empty chamber (prior to storage, for example) by holding back the hammer, pulling the trigger, and carefully lowering the hammer. But Kimber's manual explicitly says to not do that; just pull the trigger and let the hammer drop. My amateur sense is that people sometimes worry about things that don't matter much.