Here are factors to consider when specifying lavatories and vessels.
The pedestal base may be open all the way down the back, may be solid up to 16 inches off a finished floor or may have a horizontal support bar connecting both sides of the pedestal base somewhere along the back. These last two fixture designs may interfere with the drain location. Therefore, read the manufacturer’s specifications to verify what the back of the pedestal base looks like and where the drain line should be roughed in.