Yeah, I fought with "support" about that and they kept saying that it was not possible because it would get confused and cause connectivity issues. After moving up to the "Sr support" with the argument of "what the hell is a MAC address for then", was still told it was impossible.
Had some speed inconsistencies and they sent a tech out, turned out it was just really old cable from the house to the squid. The tech told me they configure some sort of bond between the NICs, my experience with bonding NICs I still connect a cable to each NIC.
I had no issues with bandwidth, I had few servers with 2 NICs each, couple computer towers, 3 TVs, tablets, phones, nest, ring, rachio. After the old service coax was replaced I never had connectivity issues and like frieed typically saw better speeds than I paid for.
Edit: Oh and xbox, switch, wiiU.