It is not a given Apple wireless headphones will use Bluetooth, or may not use the current 'standard' Bluetooth. Proprietary tech is within the realm of possible, Especially when the industry standard is not up to par.

I have not been keeping notes, have the various Apple brand wireless trackpads, mice and keyboards been using standard Bluetooth or special sauce radio tech?

Apple also uses Bluetooth for wireless tethering to iPhone, which for me has been fairly reliable. Apple Watch uses Bluetooth to link with iPhone. Seems to work well enough?

In the newest Mac OS they are now sensing Apple Watch proximity to the Mac to provide automatic Mac unlocking, which suggests they think they have a handle on getting it to work reliably.

Perhaps Apple hardware on both sides of a Bluetooth link can be more robust than using mixed brand Bluetooth?