We thought the same thing. Proprietary or open didn't matter, because with enough attempts at something you can eventually sus out its operations and optimize accordingly (or distill, as we've seen with LLMs).

The only solid way to reduce gaming the benchmarks is to ensure they're always, always changing. Enough pelicans on bicycles, start asking for turtles piloting gliders, or rabbits pushing skateboards. Broaden the focus, not narrow it into repetitive measures.