As far as I can tell, OpenAI didn't participate, and isn't claiming they participated. Note the fairly precise phrasing of "gold medal-level performance": they claim to have shown performance sufficient for a gold, not that they won one.
This sounds very like Ferrari claiming that their cars can drive fast enough to get gold in the Olympic games 100 meter sprint.
It's more like a chess engine claiming master level performance (back when that was an achievement)