How does AAC over Bluetooth work?

This is a very technical question that I can't find an answer to.

When you listen to music via Bluetooth, a lossy audio codec is required, since Bluetooth does not have enough bandwidth to send a lossless file.

The Bluetooth spec requires devices to support the SBC codec, but are allowed to add their own. Apple added support for AAC. Codecs such as AptX and LDAC are supported by other device makers.

Now Apple sells music in AAC format (m4a) and all of Apple's mp4 videos have their audio encoded in AAC. So, AAC is obviously heavily used in the Apple ecosystem.

My question is, when you connect up a pair of Bluetooth headphones that support AAC, such as the solo3 or the AirPods, and then play AAC audio, does the Bluetooth stack actually re-encode your audio again using AAC, or does it just basically pass through the audio and just pack it up to stream it to your headphones?

If anyone knows the answer to this and can provide a reference for this, I would be most grateful.