UPDATE TITLE: "Why does RCLONE work with Drive API without credentials, while Gmail API doesn't?" to "Is it true that the Drive API does not revoke the token but the Gmail API revokes when the account password is changed?"
What does the link below say are only valid for the Gmail API? Because with the rclone application, even if the password was changed, the token was never revoked.
I don't know how RCLONE works, but at a certain point it has to make the OAuth process to authenticate your app and let it use the Drive API.
OAuth 2.0 The authorization protocol that Google Drive API requires to authenticate your app users. If your application uses Google Sign-in, it handles the OAuth 2.0 flow and application access tokens.
Now, this PHP Quickstart will give you guidance on how to use the Gmail API, there it shows how to download and use the credentials.json file.
For more additional info, read this:
