It does allow you to compare a chips behavior to what you'd expect from a public design. That's not something that just anyone can do. And if the design has a

It does allow you to compare a chips behavior to what you'd expect from a public design. That's not something that just anyone can do. And if the design has a stage with a few FO4s of latency free and some unused silicon in the right place they could still put in a secret feature without anyone noticing. But it's got to be a pretty simple secret feature for it not to be obvious what's going on.