Every time I have changed tires, the odometer readings on the route to town have remained the same.  Tread depth does not affect tire revolutions per mile, the cord length does.  Cord length will vary some with tire pressure but typically 0.1-0.3% (.06-.18 mph).  It is not uncommon to see the same size tires from different manufactures or different models from the same manufacture that have 1-3% variation in revolutions per mile.  Run the same make, model, and size of tire and a new tire and worn tire will have the same revolutions per mile unless you break a cord in the tire.