Hidden Power does not have a power of 60. I'm convinced it still uses the IV-based power (30~70) from gen 2 to 5. For illustration, non-STAB Mud Shot (power 55) from Tympole did almost twice as much damage as non-STAB Hidden Power (Fighting). This being a Shadow Monster, its IVs are 20/20/20/20/20/20, which previously corresponded to a HP power of 30. Target was a Wurmple, which resists both ground and fighting.
I like Voltorb Flip, but a defective TM Hidden Power was not why I played it for 4000 coins.