When I posted that question in the AKG boards, I was disappointed in the reps answer.
The good thing is... The rep was probably wrong. I bought these anyway. And while they don't appear to support aptx (in any variety) I can pretty much confirm that they do support AAC.
I tried a Huawei P20 Pro with them and the Huawei clearly indicates AAC as the connection. Toggling to SBC changes the sound and the phone indicates SBC as the connection. Toggling back to AAC, a slight pause in sound and reconnects and indicates AAC. Toggling to any other codec (aptx, LDAC) produces no change and the currently selected codec (SBC, AAC) remains unchanged. This is standard behaviour for the Huawei when toggling Bluetooth codecs on the same headphone.
So it appears the N700nc do in fact support AAC.