The problem isn't revocation of end-user identity certificates. There's hundreds of millions of those floating around at any given point, so revocation happens very regularly. The issue is revocation of intermediates and roots, which involves invalidating tens of millions of certificates and often find themselves in embedded/non-web applications (financial, legal signatures, medical data exchange).

An analogy would be shutting down neighborhood streets versus shutting down major highways in a state for a hurricane evacuation. You can't test the latter at scale.