Well, I just "upgraded" from iOS 13.2 beta 4 to the final release of 13.2, connected my Sony WF-1000XM3s to my iPhone 11 Pro Max, and tried to record a voice memo -- and the Bluetooth connection dropped almost immediately. And a second time ... and a third time. As before, this problem is persistent, but happens randomly. If you record a few voice memos, the connection will drop -- and I'm sure the Bluetooth connection will randomly drop during phone calls too, making these earphones essentially useless.
So whatever seemed like it was fixed in 13.2 beta 4 is now certainly broken again in the final release of 13.2. Also, when I connect Bluetooth earphones to my iPhone and check the connection speed on my Mac via Console I find that the earphones are generally connecting at low connection speeds -- 160kbps or 192kbps (in the case of the Soundcore Liberty 2 Pros) or even 127kbps (in the case of the Sonys). (The Jabra 65t's connect at 256kbps, so not all headphones have horrible connection speeds.) The effect on the sound quality of low connection speeds is very noticeable -- Apple Music sounds like it's transmitting 128kbps MP3s from 2004.
When I connect the same earphones to my 10.5" iPad Pro, the connection speed is generally rock solid at 244kpbs or 256kpbs. Also, this is my second iPhone 11 Pro Max and the first was just as bad -- so something is very wrong with Apple's Bluetooth implementation on the iPhone. Frankly, I'm not optimistic that this can be fixed with an OS update -- since these problems have persisted through several iOS updates, it feels more like the problem might be a hardware flaw in the iPhone's Bluetooth implementation. Ugh.
I have the new AirPod Pros coming on Thursday. I'll bet the connection on Apple's own earphones is rock solid. We'll see. But I have numerous pairs of non-Apple bluetooth earphones that are essentially borked at this point. Very disappointed in Apple.