As far as speculating on what's going on is concerned, it's actually highly difficult to NOT notice many of the obvious hints that there's some kind of civilization outside of the wall.
Like, Zeke's baseball terms alone... Or his ace shot put throwing form in the first episode of this S3P2.
No, Isayama expects you to understand it by the time he reveals the basement. He does that constantly, by the way, where major reveals are often strongly hinted at by the time you get there. However, the extent of what's revealed often ends up being much greater than anticipated and there are usually a lot of other things brewing up already, too.
Like, in e.g. the episode where Annie is finally revealed as the Female Titan, she's outright shown lying in her bed with Female Titan Bed Hair™ at the beginning. At least by then you kinda have to see it. But the actual surprise in the episode is then that the others already know about that and prepared a trap for her.