I can kind of see what people are saying if pointing out that Gardenia didn't count, given that I don't think Ash even knew she was the Gym Leader yet when he fought her the first time, but still, he did outright lose that battle using both Turtwig and Staravia. And I definitely think Fantina should count, his Gym battle with her was absolutely treated as a rematch rather than being a "true" battle following an "unofficial" battle. I kind of hope Ash loses to Valerie too, just because he frankly doesn't have an obvious counter to Trick Room unless Pikachu's Static activates or Fletchinder turns out to have Gale Wings. Plus I admit I'd like Spritzee to be evolved for the rematch, but that's not really a big deal.