Article says they can stream unencrypted video which certainly could be done via NAT traversal without sending data to the cloud. There's plenty of appliances that do that. It's also possible they thoroughly encrypt the data at rest but just don't use https because that's tricky to do without static IPs/hostnames. Not saying Eufy is off the hook but I'd like to see a little more technical of a breakdown.
They at the least upload thumbnails to the cloud, which would include photos of the areas being recorded and people's faces. If this is part if a notification system, that probably includes timestamps. That's enough to begin to build a profile of the user, patterns regarding visitors, etc.
