I have worn right side up shoulder holsters, upside down rigs, and point to the rear types. Usually with a larger handgun, and yes, you need a jacket/coat. They were comfortable even with a heavy gun that will make yer britches droop, when nature calls and you go drop trou in the men's room, your gun does not hit the floor and slide two stalls down.
Drawbacks? Well, did have a friend that, when drawing, snagged his shirt with a sharp hammer spur, and ripped half the front off his shirt......
Depending on the particular holster/gun/jacket, may tend to "print" more than an IWB type. You wind up doing a crossdraw, which can be a smidge slower to come on target.
What we have here is... failure- to communicate.