Not getting full speed between ASUS RT-AX58U Router and Motorola MB8611 Modem

So I recently had my internet upgraded to 1.2Gbps. I already had been using the ASUS RT-AX58U Router for the excellent WIFI 6 coverage in my apartment, but since my previous modem was only a DOCSIS 3.0, I decided to upgrade to something that could support the full speed of my new plan. After some research, I picked up the Motorola MB8611. 

After getting the modem activated I noticed that the ethernet port's light on the back and the ethernet icon light on the front were both indicating that the modem was not connected at 2.5Gbps. The speed I'm getting through ethernet connected to the router is ~900Mbps, and about ~600Mbps over WIFI 6. Not exactly what I was expecting. I know the RT-AX58U supports better speeds than this, especially given that my phone shows the wifi network connection to be 2.2Gbps. I at least would expect that my wifi speed would be closer to ethernet, or am I mistaken? Maybe there's something in the settings that's created a bottleneck? Or does the RT-AX58U just not support 2.5Gbps and so i'm limited to that ~900Mbps? If so, why aren't my WIFI speeds better?

When I connect the modem directly to my computer I get the type of speeds I expected, ~1.1Gbps and the ethernet port and icon light both show that the connection is at 2.5Gbps. (connected to the onboard ethernet of my ASrock B550 Phantom Gaming-ITX/ax which I know is a 2.5G LAN port). 

Looking for any insights! Thanks!