He's confused an inode (file object) with an inode number (the index). But who cares? This is not a useful interview question.
His confusion carries over to the stat question, because he's still thinking an inode is just an index. That said, I wouldn't describe stat() as returning an inode, either... it fills a stat struct. That's all. Inodes can have more or less information than is present in the standard stat structure.
If this is how Google interviews director candidates, they've really gone downhill since I last tried to interview there in 2011 or so.