Hot Take: the proactive action of the registrar here is probably more beneficial than the number of false positives captured. If the registrar is aware that Google is hot on blocking potentially harmful sites, it's right that they take action expeditiously.

The bigger problem is the unbanning - for which there should be a better system, probably that should take the form of the registrar having a short grace period to aid in the Google stuff (DNS verification etc.) with additional checks by the registrar to make sure it's not being used for spam/malicious content.

The other point being why was Google banning you so quickly? This is the opaque part. Was the site reported? Was there some URL hijinks? That's the thing you'll probably never find out.