Overdrive is not only about rotational speed, but about ROLLOUT (distance travelled per each clutchbell revolution).

2-2.5mm tire split is used not because of the wear issues, but because it is required with 24t pulley to get 1:1 overdrive. Since with 24t pulley the fronts rotate faster, they have to be smaller to get the same rollout as the rears have.
Equal size tires with 24t pulley would result in terrible overdrive.

The reason we use smaller fronts and 24t pulley instead of equals and 25t is handling. Basically, smaller tires offer less lateral (=sideways) grip, but are more consistant. Also the suspension geometry changes with smaller tires (arms/axles sit lower, this gives higher front roll centre). This just feels better most of the time.
The only time I use the 25t pulley (and equal size tires that this requires) is when it rains and I'm running Pit rubbers or when it looks like it will be raining 10 minutes into the final Although I have tried the 25t side and equal size foams on a dry loose track and found it quite usable, I like the consistency of smaller fronts more.