MCY is narrow and short, so the potential for inadvertent misjudgement is real.
Without knowing the facts, having an aeroplane with an undercarriage problem, even if it is just an inspection that might require a gear swing, is problematic, so a quick divert to Brisbane is not such a silly idea.
If he/she had a real concern around the safety of the aircraft then Brisbane with better services again isnt such a silly idea.