Your PI2 rounds to PI1 under the rounding mode used at compilation time. Print it out with "%50.48f" (or FORMAT(F50.48)) and you'll see PI1. But PI1 is independent of rounding mode.
Sure. I thought you were implying more than that. When you called it a bug I thought you were implying that the use of one over another would alter the output of a program. My bad.