I think this is just too simplistic a take; Arc-AGI-1 was wide open to all models, harnesses, etc, and had quite a lot of innovative structures implemented by hobbyists. At the time, this was seen as a good thing (it was), because we don't know the best system architecture for all sorts of problems right now -> innovation is good.

The games are designed to allow assessment of a system. Knowing better systems to solve the games is a step forward. If any of the frontier labs could have one-shotted -3 in March with a custom harness, they would have done so.