I agree with that. The same gun in one holster may be deemed inadequately concealed and rather conspicuous while it seeming disappears in another holster even with the exact same clothing. I have really come to appreciate the value of a quality holster.
Another thing when people talk about what does or doesn't conceal, is that people often have different ideas of what constitutes concealed. Some people are talking about (and may have very good reason for requiring) no hint what so ever that they have a gun and zero chance that anyone will ever get any indication that they are. Others don't worry about slight bulges or printing or exposure of lifted shirt. I know I find myself falling into both ends of that spectrum depending on the circumstances, namely where I am going.