Yes, but that is an unnecessary confusion. A 'ground loop' is actually a voltage divider, and understanding that aspect is much easier to grasp when learning. The fact that there is a loop is tertiary to understanding why and how the ground level is different between portions of a circuit. Once the grasp the true mechanics of a grounding issue, then the loop aspect is relative.But it is a "loop", that's why smart people call it that.
It's where a circuit has more than one ground path back to the source, making a loop.
This can cause an unintended or circulating (If from the AC mains) ground current, which generates a noise voltage in the ground resistance.
In the TS's case, this is likely the signal ground between the Bluetooth and the amp.
Some of the Bluetooth noisy power supply current goes through the amp ground back to the supply, causing the observed noise.