With all due respect to your buddie's uncle, I fail to see how cold water increases resin production. Perhaps it causes some purple colors to show themselves, but that's a natural response to cold temps. There are preventative things we do to keep plants healthy and bring out their full potential, but there are no ways to coax extra thc production beyond it's genetic limitations.
Consider this: If it were true, then why would it matter if you did it the last two weeks of flowering? Why not get things jump started and do it in the first two weeks? Because if you did, you'd end up with a necrotic stick by week 8. Test it on two identical clones, give one water warm enough to swim in, and the other the cold bath, see which one fairs out better.
Again, I'm certainly not trying to argue or be sarcastic, just my thoughts.