I was one of the "special" ones who didn't make it past Google's final hiring committee review (although I now suspect this is a lot more common than they let on). And that happened after the recruiter had already called to check my references, matched me with a team, given me a verbal offer and told me it was "basically" final. The entire process took over 3 months. It has been years but I'm still annoyed by how they wasted my time.
Yeah, I was brought back after the final interview to do another round and was verbally told by the recruiter that everything looked great and that she would be extremely surprised if I didn't get an offer.
Being brought back to do another interview is not a good sign at Google. Best case is your interviewers totally forgot to cover something important, but more commonly it means somebody has serious doubts about something and they need to check it again.
Or that you're being considered for a similar job but under a different hiring manager.
Another thing to note about Google hiring is that it's very different for different role types. Specifically, for SWEs, Sales, and other roles that are expected to function in a largely boilerplate manner, it's fairly cut & dried how things work, but for roles that are less clearly defined (for example, "program manager" or "solutions consultant") the actual responsibilities can be so highly variable (or so niche) that interviewing for them is a specialization in itself. These kind of one-off situations is where Google's "automate all the things" general mentality falls apart.
Same thing happened with me -- I wouldn't quite go as far as receiving a verbal offer, but had been discussing compensation and they were asking about my other offers to send off to the comp team after I matched with a team. Such a long, drawn out process to come up with nothing.