I don't like it.
They are trying to tax an industry that really has not had any impact on the roadway system yet and there is no way to evaluate that impact at this early stage of the EV market. If that is what they want to do, then they should apply the same mileage formula tax to all vehicles and see how well that flies.
At least all drivers would be treated equally then and EVs not signaled out for a problem that does not exist yet. Plus, such a tax would likely cause some potential purchasers to defer their EV purchases, if they were already just sitting on the fence trying to make up their minds.