For anyone not following the the link, cptskippy has given a user perspective that summarises things nicely in my view:

“It's easier to tell when you're not using BLE. :) The Tesla Model 3 uses traditional Bluetooth for phone calls and streaming but the Phone as a Key functionality is BLE. When you walk up to the car and try to open it and the car says FU then BLE isn't working. When your Xiaomi Mi Band smartwatch hasn't buzzed all day but you pull your smartphone out of your pocket and have 8 missed calls, 100 messages, and 500 emails then BLE isn't working. When you're at a Tech Conference and the Conference App uses BLE Beacons to help navigate you indoors and it can't determine your location then BLE isn't working.”