"An official transcript must be issued from the Office of the Registrar, and contains an official seal or signature of the Registrar and a watermark. It is sent to ADEA AADSAS directly from the Registrar in a sealed envelope. Transcripts issued to students are considered unofficial and are not accepted by ADEA AADSAS. Also, any transcripts that are sent from the applicant to ADEA AADSAS are not accepted."
I believe that means it's not considered official even if it remains sealed. Probably because seals can be forged. So if it's forwarded directly to them by the registrar, it decreases the chances of that happening.