Google's answers were judged by IMO. OpenAI's were judged by themselves internally. Whether it matters is up to the reader.

TheZvi had a summarization of this here: https://thezvi.substack.com/i/168895545/not-announcing-so-fa...

In short (there is nuance), Google cooperated with the IMO team while OpenAI didn't which is why OpenAI announced before Google.