No I wouldn't cancel my exam at the hint of rain, but then again I am not in the position of having to travel over 250km of coastal road during the worst wet season in 37 years with known flooding and road cuts between me and my exam centre. If I WAS in that situation, I'd probably investigate my options a little earlier given the known policy that ASL has (just like this bloke has, albeit a little late according to the policy).
FYI the flooding in Maryborough peaked on sat and more rain has meant a second peak is likely today. Also the Mary River has been expected to cause flooding and road closures in and around Gympie since late last week.