And by suspicion they mean "our algorithms see something weird that might be a signal of wrongdoing or not. So just in case we shut you down"

This does not just apply to shutting down accounts - this also applies to whether to refund money due to borderline fraud by Google. Google is hostile to all customers, I do not trust them when it comes to monetary transactions based on my own experience.

GDPR actually asked for a "right to explanation" in these cases. The actual implementation is different from one country to another.

Of course, the actual practical translation of "matter of policy" is probably more like "way to save money on support staff".