Yes, the coast line follows the official admin boundaries.
So, although the Portuguese coast line was based originally on the Prototype Global Shoreline (PGS), it has been updated to coincide with the official boundaries, based on CAOP: https://www.dgterritorio.gov.pt/cartografia/cartografia-tematica/caop

There probably could be some corrections in some places, but that would need to be based on official data and not on satellite imagery.
If you want to propose changes/updates/corrections to the coastline, the Portuguese community can be reached on the Telegram channel:
https://t.me/OSMPortugal

Or in the Portuguese section in the community forum:
https://community.openstreetmap.org/c/communities/pt/176

Regards,
António.