You can find solutions for a / b / c, or b / c / a, or c / a / b, any combination of them and the solution will be correct according to the problem description.

Besides, what's does it even has to do with it concluding with confidence: "The fundamental issue is that division tends to make numbers smaller. It's mathematically impossible to find three numbers where these operations result in the same value."?

Moreover, addition is commutative so it doesn't matter what order the division is in since a/b/c = a+b+c = c+a+b = ...

So I'd say that the model pointing this out is actually a mistake and it managed to trick you. Classic LLM stuff: spit out wrong stuff in a convincing manner.

  numbers divided together  
    ↓----------↓ 
    ((a / b / c) = a + b + c) ← numbers added together
  | ((a / c / b) = a + b + c)
  | ((b / a / c) = a + b + c)
  | ((b / c / a) = a + b + c)
  | ((c / a / b) = a + b + c)
  | ((c / b / a) = a + b + c)
  | ((a / (b / c)) = a + b + c)
  | ((a / (c / b)) = a + b + c)
  | ((b / (a / c)) = a + b + c)
  | ((b / (c / a)) = a + b + c)
  | ((c / (a / b)) = a + b + c)
  | ((c / (b / a)) = a + b + c) = true