I've had two emergency brakes this year.

One because a car failed to see me while I had the right of way (and I was going at a reasonable speed since I was coming of a bridge). The only thing you can think of is 'Brakes ... now!'. And then you stop instantly but the momentum will cary your body forward thus making you fly (half) over the steering wheel. However your feet are still attached so you do a very stupid looking thumble with the whole bike. But I did break in time to miss the front of the car with minimal damage to me.

And the second time because (unexpectantly) a car did an emergency stop right in front of my nose. And I had to pull the brakes real hard to prevent me from going through the rearwindow. This time however I was able to catch the forward/side movement by managing to remove my left foot (somehow )

If you really really need an high emergence brake then just that your chances because the alternative could be worse. And I am still amazed how fast these current road brikes can stop, almost instantly ...