As far as I know PGC uses OpenTopoData.
The underlying data is an overview of manageable services. It is an existing dataset summary and seems to be the best for each area. Kartverket for Norway, LINZ for protection and EUDEM for Europe.
ArcticDEM strips of 5 meter mosaics across all of the land north of 60° latitude, including Alaska, Canada, Greenland, Iceland, Norway, Russia, and Sweden
So not PGC is responsible for the elevation data. It only uses the ArcticDEM for Greenland.