I have heard the same stories with all sorts of new plug designs. Remember tons of people reporting all kinds of advantages running Autolite plugs in oilheads? It just wasn't so. Still isn't!
Tracking one hp gains is more complicted than swapping plugs for another run. Oil temps and engine temps need to be duplicated not to mention tire temps and traction and that's just the tip of the iceberg. All that takes time and equipment that most for one reason or another don't have. It's hard enough on an engine dyno, let alone wheel dyno's.