> Why are clients being sent that extra data in the first place?

Because FPS games don't run in lockstep. They run in server ticks, which the client interpolates or even extrapolates with prediction for smoothness. This means the server has to send player positions a bit earlier than they would be visible via strict occlusion culling.

If you tried to run FPS in lockstep it's atrocious. This is literally why John Carmack originally implemented client side prediction for QuakeWorld. Do you think he was just too stupid to do the obvious simple correct thing? Or maybe the problem is actually a bit more complicated?

Again, hnews is anchoring on aimbots when that's by far the least interesting way to cheat.