Then we've got this 2013 article saying that Google doesn't care about GPA and test scores: http://www.businessinsider.com/how-google-hires-people-2013-.... Maybe things have changed since your experience.
Google's interviewing process used to be extremely absurd. They have reformed it somewhat since around 2013.
I'll admit I was an outlier - Most people around me had fantastic college resumes (And I was very lucky to have them to learn from to shore up places where I had weaknesses). There may also have been a different hiring track and bar for SREs. I didn't find it a problem then - But, given the known fickleness of HR (At my office, our best recruiter was forced out because she spent too much time hanging out with engineers outside after-hours) and the way Google has gone downhill since then, I'd not be surprised if this was now the case
What might be the rationale for that? At every company I've worked at, the best results came when people worked across divisions between boundaries. I once asked a VC what grassroots indicators they looked at inside of companies, and they said a collaborative environment without a lot of silos. I'd never heard of companies actively punishing this kind of thing, but I totally believe you that it happens. Why would they do that?
It's a sad story, but what can you do?