Sure it does; that USB port is not just for maintenance - the SU-G30 is a full MQA decoder, and its USB-B is indeed to be used for high-spec audio exchanges; otherwise I would not have bought it.
The only reason I am not able to test it now is because I am waiting for a fix to its OLED display (got unlucky, as two lemon units were delivered to me).
This is a DNLA network player too. I’d make absolutely certain this is MQA certified over USB. I have a device that is MQA over network only despite having a really good USB connection.
It is - before it broke I had already used it many times for MQA content (the screen displays MQA Studio and so when applicable); in fact, bit rates and so on are highest through the USB port.