Once upon a time, I tricked Facebook into showing me all the posts by making a list called "Everyone" and putting everyone in it. Now I'm pretty sure that it's trying to "en-smarten" that feed too by leaving off things that I think should be there (because I do see them in other of my lists).
No specific evidence of this via screenshots or whatnot; it's a gut feel. But it makes FB less interesting than it was. It may be because of a drop-off in use among my cohort, though.