Yes, in the aggregate, gas taxes don't cover maintenance; but, as I said in points 1) and 2), the typical urban sedan driver is still overpaying since they cause virtually none of the maintenance costs (by percentage). (AIUI, any cab taxes exist to fund the regulatory costs, not the excess wear they're causing.)

Furthermore, the point under debate was whether Uber, as a cab[-like] service is underpaying for its road usage -- relative to the typical person -- by driving so much more; that point is still wrong because their per mile costs are unchanged with such higher usage.