As far as juicier and more tender, I am going to have to call BS. Chicken (and other meats) gets more tender at higher IT's, like 180 and such. Plus, since pretty much all chicken you can buy these days is pre-brined, or people brine chicken themselves, there is absolutely no reason that chicken cooked to 180+ tenderness will not be so juicy it dribbles down your chin.
Now, I've not done chicken like this, so I could be wrong. However, my own testing on many different meats has consistently shown that meats, even meats generally considered tough (like brisket) can be tender if cooked to rare or medium rare, but after that it starts to toughen up. At 145 you are definitely in the tough zone, and meat does not begin to soften up again until it hits around 180+.
So if he said it was tender in rare to medium rare temps, I would believe him but I would never eat chicken cooked to those low of temps. Once you pass those temps though, particularly when you hit temps over 140*, all experiences and testing I have ever done indicates that the meat will start to toughen up after 140* and stay tough until it starts getting over 180* where it loosens up (this goes for all beef and pork I have ever tested it on, both fatty and lean cuts).