New features don't have to mean slow down, especially if those features aren't being used. Believe it or not there was a time when release notes included things

New features don't have to mean slow down, especially if those features aren't being used. Believe it or not there was a time when release notes included things like "sped up x 10%, reduced file system writes by 50% in y". Developers used to respect the limited hardware resources of their users.