This is inaccurate when applied to AirPods or other good Bluetooth audio products manufactured in the last couple years. It is accurate for products that only support SBC, though.
Bluetooth A2DP supports AAC and AirPods support AAC. Apple would never have released them if this were not the case, because they would sound awful.
That’s what’s happening.
It’s not like Bluetooth uses the AAC codec, it must be decoded and reencoded.
I’ve done a direct comparison and the deifference is clearly audible.