I hope they leave this "bug" in. I only use it when I am having a hard time grinding out the last couple of levels, but when I use it, it always seems to turn out for the better as far as the song goes. Case in point, "Gone Away" by the Offspring. I used it to bounce the verse and bridge parts and it made my play a LOT better on the song, since I could concentrate on 100% of the notes rather than grinding the level.
Off topic, "Gone Away" is now my favorite song to play in the entire game.
Thank you for releasing this information. I currently have a separate Rocksmith profile set up so that I can use this trick on certain songs that I haven't mastered on my main profile. My brother has been playing guitar for over 10 years and he sometimes messes with Rocksmith just to see what the program is like. Seeing and playing the nerfed versions of songs on my main profile has thrown him off when trying to play songs he has mostly memorized from tablature especially if the sections are drastically different than the mastered counterpart. This way, I can level those specific songs (Megadeth and Pantera DLC tracks) so he can have a experience that is closer to his skill level.
Also, I experimented with making the leveling process go faster and I never had to fail a section after raising the mastery level to 100%. I don't know if the process would be slightly different on the console versions of Rocksmith since I am playing the PC version on Steam. My steps were Choose Section -> Level Up -> Set Mastery to 100% -> Exit -> Reset Difficulty. It was also nice to find out that you can wait until the trick has been performed on all sections of a song before resetting the difficulty to bump all sections to 100% in one shot. Going back and forth for each section would have taken a lot of extra time.
Cool. Thanks for the info. This must be why sometimes I get levels bumped up by "accident". I will usually try a section on 100% just to see how it is even though I may not be able to pass it. Then when I play the whole song it's fully leveled.