but doing so gives an edit-time error specifying that "Select: Possiblity of Dynamic Refnum not supported for current target".
Is there a fundamental reason this can't be allowed? The behaviour is presumably the same in each case, and the references are from the same place in both cases. In the case structure, the exact same references that are passed to the Select node are used, with the same True/False choice.
It's not a huge issue, but it would be a nice usability/readability improvement.