But Google probably have a lot of data about their competitors that they would like to present to the judges. Making that data public would make it look like Google is smearing the competition, I can see why a judge would agree to keep that secret.

For example, Apple maybe had an auction to bid for default search spot on their platforms. Google bid the highest as we know, but we don't know what the competition bid and Google probably want to present that as evidence that this was just a normal auction similar to bidding for advertisement spots. For example, if Bing bid 90% of the current Google bid, then it is pretty clear that Google wasn't paying Apple to keep competition out but rather paying Apple for a premium spot in a fair market.

Nobody argues that Apple is anti competitive when they pay Google to put ads on top of certain search results, so why would Google be anti competitive when they pay Apple for a premium spot? They don't pay Apple to keep others out, just for the premium spot, you can still use other search engines.