Why Spam? Google publishes two example reasons, Spam and Profanity, and for fake engagement Spam is the closer of the two, so that's the one we have you pick when you report. There's a gap here worth knowing about. Google doesn't publish the full menu. It doesn't publish what the appeal form asks you for either. You find out when you open it.
The appeal is where the argument goes. The one we prepare names Fake Engagement in its first sentence and quotes the review's own words. Then it puts what the account's public history shows next to what your records show. A name missing from your records isn't the violation by itself, so the appeal never rests on that alone.
And there's a catch. Google gives you the one-time Google review appeal, one per review, ever. You name a policy when you file. Name one that doesn't match your argument and that can waste the one appeal you have. So the filing is the whole job. You file it from your own profile. We never submit anything to Google.