David Lai just tested it and it works great. I connected the AirPods Max with a USB-C cable to my MacBook Air where Garritan CFX was running and in the Garritan's audio settings I could see the AirPods Max as an audio device and I used the lowest buffer size of 32. I can't hear any latency at all, so the promises are true, it's low-latency audio over USB-C. All modes work: active noise cancellation, transparent mode (which makes them feel almost like open-back headphones although it's still slightly awkward because it uses external mics to bring the outside noise while the pads seal your ears hermetically). The sound signature is pretty OK for closed-back headphones, however I still prefer how my open-back Sennheisers work with Garritan. Also, the sound volume is slightly low with Garritan CFX, even when the volume is maxed out, so a gain on Garritan CFX is also needed but I think that's partially a problem with Garritan which I've noticed with other headphones too.
But in any case I am pleasantly surprised since I wouldn't expect from Apple to implement something like that, you know Apple, they are stubborn and would not bring new features, they'd rather release a new product asking you to spend and spend... I can see how the AirPods Max will become a useful tool for audio producers and creators, being able to use them wired in a low-latency mode. Again, that can only work when you connect the headphones to an Apple device with a USB-C cable. As a side note, the previous version of AirPods Max with a lightning connector support an optional stereo mini jack to lightning adapter which does a similar job of low-latency lossless audio transfer, however the difference is it requires an audio input signal that goes through ADC, so there are other downsides with that approach.
