Official Change-log is below from the Google
Improvements in double tap Rewind and Forward feature.
Today's YouTube app got the improvement in it's most recent feature double tap to rewind and forwards. Google improved the app functionality to work the double tap feature smooth and faster.
Else, minor visual improvements and app speed improved also we found in this update.
Go through the below link to download the APK File of this update:
YouTube APK v 12.07.59