Would the interviewer be right?

Please avoid stating which problem these are solutions for.

During a recent discussion the following code was suggested

int desc(const Node* node, int d)
  int l = d, r = d;
  if (node->l) l = desc(node->l, d + 1);
  if (node->r) r = desc(node->r, d + 1);  // edit: thanks, Nico
  return max(l, r);
int d2(const Node* root)
  return root ? desc(root, 1) : 0;

One of the folks in the discussion shook his head and said: “If this was an interviewer, they would want you to do it in one function, though”. Then he presented this:

int d1(const Node* root)
  if (root == nullptr) return 0;
  return max(d1(root->l) + 1, d1(root->r) + 1);

Then he made the assertion “this is what an interviewer would be looking for”.