It's true. This weekend I was helping my brother with his HR8 urgent - killing Yama Tsukami.
We'd had a good run, and had flinched it regularly but had a bit of bad luck (I made Yama fall to the lower level but hadn't realised my brother had jumped down to run out and heal) and then he got my brother with his suction attack.
Consequently we were a little worried and were trying to be ultra safe. So when Yama refused to come back upto the top level I thought I would try to attract his attention by throwing a paintball at him.
Seconds after the second one was thrown it came up "Objective complete, returning to village in 1 minute) - so I'm guessing he is allergic to paint (its all that wood). :D