I don't think anyone disagrees that linearly scaling of traffic scales linearly. What they're getting at, why would you still use that rather implementing something more efficient? Like Battlefield games (bf4?) did, using different update rates for nearby and distant players.

Would also argue that RTS inputs are different from fps as in general you give commands to units, like go here in move/attack mode, and they do it for you. In fps your inputs control a character directly. So they can use different methods of conveying progress of state. And an fps game can use both methods, like doing deterministic physics for objects. Also don't need to wait for inputs just because its deterministic simulation?