There are places where a wider tyre will be faster-but that is not down to Less Friction or rolling resistance.
It is down to comfort. A rough surface and a bit of suspension is wanted to ease the body from slowing down through pain. You can only take so many "Knocks" without the terrain affecting you.
Surprised they haven't come up with a Tyre called "Roubaix" by now. (Paris Roubaix where many of the riders will run 25 tyres to ease the pain over the cobblesas well as modified frames and forks)
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How long was I in the army? Five foot seven.
Spike Milligan