I've never understood that term in a musical context, either for a guitar or a player. Do those guys have really basic guitars and don't smile much? Does that mean the rest of us have 'nonsense' guitars, and play in 'nonsense' styles? Would almost all of our guitar heroes, at least mine, fall into the 'nonsense' category? Would that make Hendrix a nonsense player? From what I can gather, I don't have much interest in listening to 'no nonsense' guitarists. I like to listen to guys that go above and beyond what's required, and take things to the next level (like All Along the Watchtower and Voodoo Child).
Not trying to give you a hard time, as it's a term I've heard a lot over the years and it continues to elude me. It's always used in a positive context, but it doesn't seem all that appealing to me. Maybe I've been conditioned by the late '60's/early '70's bands I've listened to.