That doesn't make sense; There isn't one pool of "upload" data and another of "download" data. Rather, there is one pool of data streaming from edges into the core (upload) and back out again (download). You can either attribute each chunk of data to its uploader or to its downloader, but in either case, the pool is the same size.
Edit: or these metrics don't mean what I think they mean, in which case, please tell me!
Youtube has far shorter videos (5-15 minutes on average), defaults to 480p or less most of the time and the visitor session length is much less than the average Netflix stream.
Netflix is doing 720p / 1080p defaults on most players, 1 hour to who-knows-how-long non-stop sessions (I personally have binge-watched like half a season of TV shows in one sitting occasionally) and gets daily recurring traffic from multiple members per household.
Right, what I meant though was YouTube let's anyone upload videos. That ingestion must account for a lot more than Netflix's TCP ACKs considering 100 hours of video are uploaded every minute to YouTube [1].
Edit: or these metrics don't mean what I think they mean, in which case, please tell me!