Yeah that is perhaps the most problematic aspect of Bluetooth. The radio interface is designed with the presumption of the signal bouncing off nearby surfaces. Thus it is sensitive to line of sight issues.

Mind you, i have also been able to connect to a USB dongle through solid wood walls, so mileage may vary.

Never mind that you can get two classes of radios, on top of the LE stuff. With each class having different transmission strengths.