In Counter-strike there are footstep sounds with spatial audio. How can the server not send that info to me in a way that won't reveal the player's direction? hearing players coming before you see them is a huge part of the game.
Think about many times a second you have to trace a shot.
Now think about how many times a second you'd need to trace from every pixel on the screen to every part of the geometry on every opponent in order to check if it was visible or not to see if a player was legitimately able to view any part of their opponent.
If you actually understood your own link you would see that there is no reason to trace every pixel on the screen when you can make a bounding box that covers motion and trace the vertices.
Anyone familiar with game engine programming would never consider what you are saying. That link is a more in depth version of what I just said, ray casts are being done on the server for visibility and have nothing to do with rendering the game to do it. It is literally demonstrating that they are already doing what people were wondering about.
A bounding-box is something we'd call an over approximation.
Using an over-approximation causes the opponent's location to be revealed to the client even when the opponent isn't quite on screen yet, requiring the client to be trusted to not show this information early, which is what people in this thread want to avoid.
That's the whole point of the discussion.
This is what the article is showing - can you see how the red outline of opponents appears early, and how the client is being relied upon to hide them until they're actually visible? That's what people don't want.
You for some reason are ignoring what you originally said to focus on something else you are seem to misunderstand the context of.
What you originally were saying was that you would have to render polygons in hardware for the server to have any idea about occlusion, which the link that you gave not only disproves, but assumes that no one would think in the first place.
The whole point is that wall hacks let you see people running around the whole level and it is just a matter of work for the server to only send positions a few frames before you are going to see a player.
Everyone else is on the same page, but you think the player position being sent right before they appear is a problem? That's the solution in your own link.