"when loading the weapon, load from the magazine and do not drop the round directly into the chamber." So what's the difference if you drop a round into a revolver cylinder vs a pistol barrel? Also, why would it make a difference if the round is dropped in or rammed in from the pistol slide?
That's generalizing from a rule that's true for most (but not all) autoloaders.
My Ruger P90's manual, for instalnce, specifically recommends dropping a round in the chamber for single loading.
"As was the man of dust, so also are those who are of the dust, and as is the man of heaven, so also are those who are of heaven. Just as we have borne the image of the man of dust, we shall also bear the image of the man of heaven. "