When you are supposed to have received an exotic DX call on 6m JT65 it is worth looking to see who else copied the call and in what area. Some of the calls supposedly were seen only by me, suggesting false decodes. When several others spot the same DX call it is often a pirate nowhere near where the DX is supposed to be.
Some really long 6m JT65 DX is genuine: for example the 13 (thirteen) Japanese stations spotted a few weeks ago were genuine, but one has to be careful. Some exotic calls are actually pirates just down the road.