Not seeing improved upload speeds after upgrading to a Netgear CM2000 DOCSIS 3.1 modem

I’m on the gigabit plan and my download speeds were as expected with my previous DOCSIS 3.0 modem and with the new Netgear CM2000 DOCSIS 3.1 modem. 

However my upload speeds are the same, around 23 Mbps. 

I spoke with support today and they said the modem is provisioned and everything looks good on their end and said there must be an issue with my modem and suggested, of course, that I use their hardware. 

The Netgear CM2000 is on the list of supported modems for Xfinity and that’s actually how I picked it as one to buy. See https://www.xfinity.com/support/devices

That page even shows that my current modem is the CM2000. I purchased this brand new last week.

My issue seems similar to this post: https://forums.xfinity.com/conversations/your-home-network/sb8200-modem-not-achieving-100-mbps-upload-speeds/657a6693e4ada534519226cf

Unfortunately that user’s issue didn’t seem to get resolved.