[CynicalC]

When an engine is cold, fuel doesn't ignite as easily as when it's hot. It tends to condense and get blown right through the exhaust unburnt. This is a lean condition. Using the choke enriches the mixture with more fuel to correct the imbalance. Whereas just twisting the throttle doesn't change the mixture, it just increases it. To put it very simply, twisting the throttle doesn't add fuel, it adds air. The carbs add fuel to compensate.

Now whether any of this matters is another story, but it doesn't make any sense to twist the throttle to keep a cold bike running when that's the sole purpose of the choke.