The different devices look like one device by being a "coordinated set" in Bluetooth parlance.

Each member of a coordinated set gets its own Bluetooth battery level slot, so there's no problem here. The spec supports this use case natively.

It seems the the right answer shouldn't be "none of them" though.

So which one should it be?

Whatever is reported to iPhones. It's not an excuse to block non Apple devices from reading battery level

All three get reported to iphones.

That’s not part of the Bluetooth spec to report battery power for three separate batteries on one device. Where would it be reported to?

Yes, that's my point.

If it’s not part of the BT spec - how is Apple going to report three battery levels in a way that’s compatible with non Apple devices?

Again, that's what I'm saying. We are in agreeance but you really seem to want to argue.

Minimum between L and R.

The lowest one among the two earpieces?