Yeah, like Glenwing said, the DP standard got a bit messy. They're not wrongly wired, the standard just changed dramatically making old-type cable cause displays to flicker due to a changed use of a power carrying wire (pin 20, I think it was). Safest bet is definitely to get a certified or at least a brand you've googled to be conformed to use newer wiring.
Version 1.5 (2.0?) is incoming this year, so brace yourself for any changes.