I've heard that mentioned before, but haven't ever seen any laws to that effect.This would be a state issue. The three states where I spend most of my time have both licensed CCW and unlicensed open carry and there is no requirement to keep it concealed just because you have the license.
I've carried in many states and I try to figure out all of the laws there before I go. Because of where I'm going and what I'm doing there (mostly for work), I am always very careful to always keep it well concealed, so I haven't looked specifically for prohibition on "printing" or coming uncovered in those states but on the other hand I don't recall having seen that while reading through laws.