I'm really excited about this, although it may have been around since iOS 14, I don't know. But I discovered a setting under each bluetooth device where you can specify what kind of bluetooth audio device your given bluetooth device is. i'm in the minority here, but I always had a huge beef with voiceover audio being routed through the phone's speaker with iOS 13, because I couldn't adjust the volume of voiceover like normal. I have a bose sound wear companion, which is a cross between a bluetooth headset and speaker. I really had issues with voiceover being pumped through the phone's speaker, because audio on the soundwear is close enough to my ears where I couldn't hear voiceover from far away if it was coming through the phone's speaker. Anyway, you go to settings, bluetooth, choose the device you want to set what type it is (it doesn't even have to be connected at the time, in fact, it's probably better if it's not, then you'll have to restart the bluetooth device). Once you find the device, swipe down, to where it says more info, then double tap, and one of the options is device type. Options are car stereo, hearing aid, speaker, headset, other, and there might be another, I don't know.
Hope someone finds this info helpful, I'm really excited about it!!!! :)