The stated yardage on the 10th on Merion is measured along the centre of the fairway and then left through the dogleg - 270 from the front tees. But if you cut off the dogleg the real yardage is 240. You can determine this by adjusting your tee shot and mousing around the hole.
The short par 3 13th plays about 10 yards shorter than the stated yardage, perhaps accounted for by hitting the ball farther from the teeing ground than the fairway + being a little downhill (but in this case I think the hole is 'juiced' by WGT to play shorter and bring the bunker behind the green into play).