It's undersquare. Show me a stock internalled EA888 that'll spin to close to 8000rpm.
A stock internal one wont, but not for stroke issues. You could upgrade your bottom end and valve train and cams and turbo, and make power to 8 grand and the motor will spin to that just fine. The reason you wont make power to 8 grand is because you'll never run a set up or have software that will allow you to push the motor that hard, unless you get custom tuned, which the vast majority of people dont.
It has nothing to do with the bore to stroke ratio, or whether or not its square or undersquare. Its the rod length to stroke ratio, which is determined by sufficient or insufficient deck height to maintain a long enough rod to accommodate the stroke, keeping the angle of the rod at the 3 and 9 oclock position at or under a certain angle.
Between the two of us, Ive built motors.