To be fair, the way SPN was defining ghost sickness was not really related to fear of death per se, just fear in general. But I don't know where they came up with Japanese ghost sickness, and I couldn't find any reference to the buru buru googling around, so who knows what they were thinking.

They've demonstrated before that they don't, actually, give much thought to how their racial politics come across to viewers, so I can't say I'm too surprised.