You could have said it's a function CR x CR -> 2 to refer to the Computable Reals. Instead you explicitly made it about the reals R, making it hard to be charitable.
Yes, they could have made their comment more accessible and mentioned the encoding (but I think then the problem may have sounded less "natural", since you'd have Turing machines mentioned). But you also could have noticed you're building a strawman argument, and instead just asked how does one encode Reals. Heuristics: if other person's argument sounds too absurd, there's a chance you're misunderstanding something.