My feeling is (not 100% sure though) that the restart is needed only to make titles/descriptions and other text resource specific things work. The UI is loading the text resources only once at startup time, that's why a restart is needed.
If you change metrics and other stuff in an existing report I think it should be reflected without restart.
My suggestion is:
1) try only the update script.
2) if changes are not updated - restart
Hope this helps,
Alex D.