If one has such an issue with retention then I would say that they need a better holster. Also the position of carry should be questioned for why they're putting the gun past a 90 degree angle from their front (then again even if I am concealing I'm not a fan of carrying it on my back area). Now yes it "could" be used as a type of retention, but I would say if that is why you're covering it then you need to recheck your reason for doing so as it seems an extremely weak reason to me.
Personally I carry at the 10-11 clock position and don't worry about things like bending over. I also don't worry about if I put on a jacket and if it covers the weapon or not. I just proceed to go about my life.