Even in the West, nobody of low seniority challenges the C-level executive when they tailgate or walk around without their badge. And if you are new, if there is an important looking individual you don't recognise, you leave him alone, totally validating the "act as you belong adage".
Exactly the wrong message to send, particularly for an agency that’s supposedly an expert on security.
A signature (or stamp) is easy to fake and get away with for a while. It's very rare that the authenticity of signatures is checked right away. Perhaps even easier than stealing or faking a not-particularly-secured stamp. It only happens when some problem arises and is investigated after the fact. The question is not whether the signature is "authentic enough" but who signed the document. You can aks and answer this question about a seal equally well.
The reason we have signatures (or stamps) is as an explicit ritual signifying ratification of a document that one cannot plausibly deny later.