The IP is well know so I'm not sure I follow the point about DNS. Also note it's not that they see 'about 5GB' but the size of every packet and exactly when they were sent / or in reply to what other packets. They can also have bots watching for all new content as its posted and who downloads files of the same size, etc. I would assume HTTPS will not stop someone from knowing what files you are downloading from a nation-state adversary.