My best guess is it relates to their "Remote Management" software which limits what connects to their internet service and that includes routers in bridge mode as they are slowly being squeezed out as they want users to use their gateways, modem/routers and more importantly where they connect to and for how long. My advice, find a small internet provider that can provide the speed, the service without the remote management software that the big boys use to control what connects and what doesn't. Fact is, I don't see there being much of a choice so either find a smaller provider or forget using your hardware. This is only the beginning of what they want to control and they're willing to spend whatever it takes to control you, what you watch and how it pads their internet bandwidth billing. There are some providers who don't use or can't afford remote management software but even so, it doesn't stop or prevent the big boys from using it.
P.S. The only other way around it is subscribe to a Private Server which will block them from knowing what you're connecting to, how or for how long. Look for a VPN provider as some won't and don't record anything after you connect to their servers.