COX sabotaging VPN traffic?

I spoke to Cox support over chat and got the company line about not supporting VPN.  Another post on here the Cox rep suggests that "once you are on your company's VPN you are no longer on the Cox network."  This is erroneous, as that is the only link to the internet from your house.

At this time, I have tested every possible connection method results below using Fast.com...
Cox WiFi - 20-30mbps
Cox WiFi VPN - 0.5-5mbps
Cox LAN - 140-240mbps
Cox LAN VPN - 3-78mbps
Verizon LTE - 10-15mbps
Verizon LTE VPN - 15-20mbps

I have the Cox 300mbps service.  I understand the LAN speed will be the best.  I also understand that VPN will slow things down.  However, the fact that my VPN and non-VPN speeds are much more comparable on Verizon can only suggest that the Cox network is degrading the connection.  All indications are that my home router provides no discrimination to traffic either so that should have no bearing on the performance.  There is no reasonable scenario where my 300mbps surface connection should be worse than LTE connection hotspotted through a tablet.

My only questions are 1) Is this a technical flaw in the Cox infrastructure somewhere in the chain, or an intentional FUBAR by Cox to encourage home office users to get Cox Business Internet service? 2) Is anyone currently using their company VPN with more than 10% of their off-VPN bandwidth?