SB8200 Max Upload Speed

Hello,

My internet plan recently changed from 800 down / 20 up to 800 down / 100 up. I own an Arris SB8200, but the max upload speed I've ever seen is still hovering around 20 Mbps. I received an email stating that I could receive 5 - 10x faster upload speeds if I upgrade my modem. The SB8200 is DOCSIS 3.1 and my understanding is that it supports upload speeds up to 232 Mbps, so I'm wondering why I would need a new modem to support the 100 Mbps upload speed.

Do I really need a new modem? This thread on Reddit suggests it might just need a firmware update.