third party can sign the document with the forwarder's signature

We noticed the following situation:
If the Adobe Sign signature request email is forwarded (not delegated) to a third party, the third party can sign the document with the forwarder's signature.An example:
1) Person A requests Person B's signature, Person B receives it
   Adobe Sign Mail requesting a signature.
2) Person B forwards this email to person C.
3) Person C follows the link from the forwarded (non-delegated)
     Mail and opens the document in Adobe Sign.
4) In Adobe Sign, person C, when clicking in the signature field, becomes the
      Person B's signature displayed.
5) If person C signs the document, Adobe Sign concludes that person B
     has signed. This is also reflected in the test report.
Although in the case Person C “signed,” the document records that the signature came from Person B.T
Is anyone familiar with such behavior?