There are probably 3 main groups of people with WiFi appliances:

1. The vast majority of people don't care, and put it on their normal WiFi router and would never notice something like this
2. A smaller group of people don't care much, but pay attention to their bandwidth usage and would spot an appliance trying to send 3.7 GB of data a day
3. A much smaller group of people are paranoid and would put the device on its own isolated subnet, or use firewall-type features to limit the access their appliances have to the Internet.

My guess is that if this were a widespread problem, people in the second group would notice, or would have immediately checked and chimed in and said "holy crap, mine is doing this too". I didn't hear many people saying that, so I'm guessing this is a bug, and it's either a one-off weirdness, or it's a bug related to people in group 3 who are blocking their appliances from being able to connect to the Internet.

It's probably something as simple as a badly programmed firmware update check that doesn't do exponential backoff when it fails. It probably connects, fails, then immediately tries again. A proper exponential backoff would wait before trying again, and if it failed again it would double the wait time down to some minimum value like once per day or something.

Incidentally, this is also why claims about smartphones monitoring people's conversations when they're supposedly off is BS. That would require either huge amounts of bandwidth to transmit all the conversations, or huge amounts of computing power inside the phone to decode the voices. Either way you'd be using tons of battery, and probably a significant amount of bandwidth. There are enough paranoid people out there that if this were a real thing, someone would have caught the devices doing it by now.