Exactly. As a general Rule, the PCs only know what's in the Players Handbook. That's also a design feature of the game - players don't need to learn the setting before playing, they can learn as they play.
This was my initial assumption based on past experience with other games, but now that the beta versions of the GM and player's guides are out, I can't see how this would possibly work. Here's a few examples of cases where the information in the player's guide is lacking details that, I feel, the GM guide indicates that the general population would know.
- the player guide mentions Rust Brothers several times, but it doesn't give any background about who they are. In the GM guide, though, it's stated that Raven Sisters (who, incidentally, aren't mentioned in the player's guide at all, despite "being very popular in villages") are "always on their guard ... since the Rust Brothers pay anyone who captures a sister for them well". How could this be a well known arrangement, but none of the characters have any idea that the Raven Sisters exist, that Rust Brothers will pay for them, nor do they know anything about the Rust Brothers other than they're a feared cult group?
- the player guide doesn't mention whiners at all, however the GM guide heavily implies that they're "commonly hunted" by humans and orcs because of the belief that their meat has healing and other magical properties. This seems like something that at least some, if not most or even all, PCs would be aware aware of. (The same is true of all the non-playable kin... I could see the players knowing only rumors and legends about them, but they just aren't mentioned at all).
- The player's guide has essentially no information about any of the gods or religions in the world, despite the opening line of the GM's chapter about gods being "Religion is paramount to the humans of the forbidden lands, above all when it comes to separating friend from foe." A few of the kin descriptions get in to that kin's god a bit, but there's no consistency at all... about half the gods don't appear in the player manual at all (and for a few, their only mention is in the stronghold chapter, where it says you can build a shrine to a god you know nothing about...). The second sentence of the chapter about Gods in the GM guide is "Most of the Forbidden Lands humans worship either the raven god or the snake god..." and then goes on to explain a super basic origin myth for those two gods. The player's guide doesn't have the word snake (outside referencing the speed of one for a spell descriptor) or Wyrm (how the snake god is sometimes referenced in the GM guide), and raven (unless it is followed by the words land or purge) isn't even mentioned in the Human kin section, but it is referenced a single time in the Elf kin chapter right after it, which is the only mention of that god in the entire player book.
I could probably go on and on, but frankly, saying that PCs shouldn't or don't need to know anything about the world when they start playing is just not possible and would be actively less fun for players and GMs, imo. Going further and calling it a "design feature" is frankly a bit of a cop out. There should be, at a minimum, a summary of commonly known history, or at least some commonly held beliefs about history, a reference for commonly worshipped gods and their followers reputations, and more information about the various kin, playable and not.