Oh come on. This is just unnecessary pedantry. We live in the real world here where people are people and not die-hard ideologues. It makes perfect sense that they do this. If youre a Facebook member you get access to the "openness" they're talking about. Plus it'd be really dumb for "to make the world more open and connected by providing an online service that lets you comminicate and share messages and assorted media with people with which you already have or will build connected relationships with if you are a member of our open connected service" to be their mission statement. Obviously the bulk of it is implied. If you follow your argument all the way through then you eventually get to ampointnwhere you're basically arguing that they explain the entire service right in the mission statement leaving out no detail. Just, c'mon. We all know what it means.
Thanks for clarifying. It's been a while since I clicked on a Facebook link. When I tried it just now, you are right that direct post URLs will work. But when browsing a public page or profile, there are pop-us that obscure the rest of the screen as you scroll or hover over links.