This article answers the question: What happens in Google Apps Script if the required OAuth scopes were already accepted and reduced afterwards.
We assume the following case: A Google Apps Script (aka Script as Web App) needs access to GMail and Drive.
The consent screen is then accepted.
Then the source code changes and no more access to GMail is required.
Will this require a different consent dialog?
No the OAuth scope is kept as already accepted and nothing happens.
If the OAuth scope is extended, this will of course bring up a new "This app needs authorization to run."-button
and also a new consent screen, where the new scopes are listed
The new consent screen:
The first consent screen:
The first consent screen with developer info:
Account permissions - Apps conntected: