Did some searching and found a teardown of the router on a Chinese website. Your correct it is a Broadcom chip; however it seems the Ethernet chipset (BCM84880) does provide additional speeds up to 5Gbe, but the processor (BCM4908) for the router does not support those additional speeds.No, it's a Broadcom chip, not an Aquantia.
Kind of a shame, but it give me hope that 5 to 10Gbe Ethernet will become more common for consumer routers even if internet’s speeds for most people aren’t up to that standard. On the LAN only side it’s promising for local network file sharing.