Fascinating. I hope you're not trolling! I'm wondering whether this will work on a recent iMac then? Has anyone got one to test?
on the handful of LG 5K's I tried, they all down sampled to 2560x1440. Using a similar spec MBPretina as the other user, same situation and even a newer 2015 15-inch spec'd out model.
Though it does not seam feasible to get 5K down a single Thunberbolt 2 channel.....