Nothing gave the appearance of being over tightened, based on the handle bar after removal and none of the three pinch bolts felt overly tightened. I used a hardened washer to seat against the pinch bolt to loosen the clamp, no more than a 2/3 turn at most on the worst of the three was required.

I think the corrosion theory might be the most likely and with one I discovered last night could've also been a small piece of dislodged casting flash. After cleaning the inside of that one and filing away the remaining flashing I reused that one and it took about a 1/4 turn of the pinch bolt to install the new handle bar.

Brad