I care deeply if something has been copy/pasted, but not for attribution reasons. I need to be certain the person who copy/pasted the code actually understands

I care deeply if something has been copy/pasted, but not for attribution reasons. I need to be certain the person who copy/pasted the code actually understands what the code does, rather than blindly grabbing the first result off of SO and exposing the codebase to vulnerabilities.