As far as I know, the tang is what is radiused (but of course I don't know a whole lot about lock geometry, I just know it works or doesn't). From what I saw, a radiused lock face is designed to be "slip proof", where the lock face looks kind of like a claw, and the raised poplars at the start of the lock face is designed to make a slipped lock have to travel up it to fail (which physics forces it into the most recessed part, making completely lock failure nearly impossible).
Sorry for the seemingly incoherent wording, I don't know a lot of the terminology.