Is pre-save possible with API alone?

[speedo123]

as a follow-up to my previous thread:

https://community.spotify.com/t5/Spotify-for-Developers/Client-side-only-for-album-pre-save/td-p/502...

does simply saving an unreleased album add it on the release date? Or is pre-save simply granting access and obtaining the token which is later used to add the album on release day to the users’ libraries?