Upload Speeds

I'm currently on a Download 800 Mbps/Upload 35 Mbps plan (Speed test shows 600/35) using my Motorola MB7621. I'm in an area offering next generation internet network.

I found this thread below which is closed that seems to indicate you can send a direct message to Xfinity Support but I don't see any option to do that (update I know see the option to direct message when I logged in the next day so I'll try that).

https://forums.xfinity.com/conversations/customer-service/upload-speeds/677b01a7121aae71d76926bf?commentId=677b05b23423b47b4071a8d0&replyId=677bd66e7699a97c89069e62

Assuming that Xfinity reply is still current, can I simply buy a one time $99 Amazon.com: Hitron CODA DOCSIS 3.1 Modem | 1 Gbps Max Internet Speeds | Certified with Comcast Xfinity, Charter Spectrum, Cox & More | 10x Faster Than DOCSIS 3.0 | 1 Gbps Ethernet Cable Modem ONLY : Electronics modem, get it configured with Xfinity, and then be able to upload at 100 Mbps instead of my current 35?