You may or may not be correct , do we need to place the sealed transcripts envelope inside the courier envelope , and couries envelope shoud not be stamped as well?
check below link
https://www.wes.org/help#/path/Credential-Evaluation/1200364261/Document-Requirements-for-India.htm
You are right, seems like they want the University to courier it to them. I guess WES will check the sender's details on the courier packet to confirm it was sent by the University and not the applicant. WES just further complicated it for you guys

Good Luck !