Buggy Bluetooth on the other end... Alexa is running Linux, and the Sony is probably some custom bluetooth stack.

Once you move to all Apple bluetooth, things really smooth out. It seems that Apple does way more testing/validating of their Bluetooth stack.

I had the idea in my head (so take with a grain of salt) that parts of the BT stack are underspecified such that different implementations tend to have slightly different interpretations of the standard, so the problem isn't even which vendor you use so much as going all-in on any single vendor so the devices all agree on which reading to use.

Although of course Apple might well be better anyways; one would hope that billions of dollars in R&D plus caring about quality makes a difference.

I've actually worked in this area. You are basically correct.

Sometimes you have to make a choice on which brands/chipsets you support. Devices on different ends of the compatibility spectrum can basically be mutually exclusive. IIRC if you advertise A2DP some devices supporting only HSP won't work, so you can make some hacky workaround but then your nicer A2DP equipment is harder to use. If you only need to guarantee support for X subset of devices you control, it's easy to tweak the settings so they work well together.

Actually the spec is overspecified and repeats itself multiple times in different layers. L2CAP specifies a TTL, so does RFCOMM, so does SOC, so does...

I buy this. All Apple works great, but Apple headset with Windows PC doesn’t seem better than anything else with Windows PC.

They don't smooth out, for me, at least. Airpods Max, for example, can just decide to transmit nothing but deafening static to the other side in the conversation.

Eh, I’m still having weird connection issues between my iPhone and OG AirPods. Less than with my old headphones, but more than I’d like