“Radar includes a rule to block any payments that fail the CVC verification check, which you can enable or disable within the Dashboard (this doesn’t affect payments where the CVC check couldn’t be performed).”

Also;

“…Support for both types of AVS checks varies by country and card issuer (for example, certain countries don’t use a postal code or some card issuers don’t support street address verification)”

So it appears there are cases where these checks can be enabled on your Dashboard, but skipped by Stripe or not actually performed by the issuer, I’m thinking like for prepaid cards?