Even with negotiations, If a engineer said in a Google youtube talk "Oreo is Americas favorite android," they could set themselves up for trademark infringement.
If Google had a line in a blog post that said, "It's better than real Oreos", they could likely be sued.
Oreo would not like Google saying either of these things. So Oreo needed to make up legal documents to map out all the things Google is allowed to say about Oreo Android. It seems like an unnecessary legal headache - one for dubious marketing gain.