No one actually knows that FrAgile, SCUM, or TeeDeeDee are universally better than just having a bunch of programmers self-organize. There's no well controlled studies that show anything other than a weak association between hip methodologies and measures like productivity or profit, and no one has demonstrated actual cause and effect. That probably won't happen because these are purely human systems, and good luck controlling for that.
It's fine to consider methodologies, but there's no reason to believe that the people who invented or tout said methodologies should be blindly trusted. They discovered something that they believe worked for them, and that's it. They're not smarter than you. Only use aspects of methodologies that you would use or that you have seen work, and don't do anything that seems stupid or that you would dread.