I wonder if the feature is bugged or something if that rly is what it means when they are dark like that, because it has happened multiple times now to post I'm 100% sure I have not yet seen.
I have all boxes checked under the setting for mark as read in Infinity, maybe they have not yet been tested enough to find all the bugs.
I believe he is referring to the fact that YouTube don't have to pay upfront for new content, they even get new content without hunting for it, and many smaller channels don't have partnership and so on.
Sure they have a platform, backend and so on. But Netflix needs to have all that too plus buy things to show to their customers.