Chris has the new iPhone XS and the wireless Apple AirPods, but he keeps getting distortion when he takes calls. Not when listening to music or watching video, though. Leo says that Bluetooth headphones have two different modes. There's a mode for use as a headset for calls and A2DP. A2DP is stereo and was designed for listening to music. Headset mode uses the minimum bandwidth possible. So that could affect it. Also, a phone call that is routed through the internet can be full bandwidth and it may be that the AirPods just can't handle it. There are some headsets that support HD Voice using A2DP mode. Plantronics makes a model that does.
Apple is also using Bluetooth 4.2, which is a bit long in the tooth. Bluetooth 5 is the current standard, and even the phones support it. Leo expects the second generation Apple AirPods will be coming soon.
Leo also says this is one of the reasons why he is angry over Apple dropping the headphone jack. Wired is still better.