Yes, i'm holding brake and kick up the revs. Is hard to say if that is harmfull. ZF 6HP28 has protection about to high revs combine with brake. After few seconds holding gas with brake, she cuts torque and revs goes down, so if starts will be not done one by one, i think that is safe.
I have same one but manual and if I hold clutch in and full gas, it bounces off 4K rpm to launch. But I haven’t done it yet because I’m afraid to harm anything haha