> to reveal both players to each client during the same tick

And I explained why this is not feasible given modern network topology. Players move around maps and peek around corners in between these "tick updates" the client gets from the server; therefore, we have to use clever methods of interpolation and prediction as well as server consensus to ensure that gameplay is smooth (e.g. models can't just pop in out of nowhere, movement feels good) while also being as fair as possible (e.g. we don't favor one player's view over another's).