Why would "which reference class is x most like" be a "failure mode"? Don't just word-match to the closest post including the phrase "reference class" which you remember.

When you're in a dark alley, and someone pulls a gun and approaches you, would it be a "failure mode" to ask yourself what reference class most closely matches the situation, then conclude you're probably getting mugged?

Saying "uFAI is like Terminator!" - "No, it's like Matrix!" would be reference class tennis, "which reference class is uFAI most like?" wouldn't be.