I believe it's just a computer-controlled brake assist that distributes brake power to wheels that are still spinning, instead of locking up 1/2/3/4 of your wheels. Keeps you from skidding out of control.
My IS brake pedal has always felt "squishy". Many people have bled their brake lines (thinking there was air in the fluid) only to still have the "problem". I don't think the EBD (specifically) is to blame but rather the ABS mechanical system. Switching to aftermarket "steel braided" brake lines (instead of rubber) might help some. Anyways - I think Lexus feels that "as long as the car can stop properly" the pedal feel is not really a problem.
The EBD system is a replacement for the old "fixed portioning" valves. When a car brakes (going forwards) the weight bias shifts forwards (unto the front tires) so cars have typically had a valve that favors the front brakes. Usually they had a fixed ratio like 60% front braking, 40% rear braking. Race cars tended to have a control gnob so the driver could manually adjust this if they wanted to change the behavior of their car. Well EBD is apparently an improvement where various sensors determine how quickly you are slowing down and vary the portioning (between front and rear) to avoid lockups (or invoking the ABS system). I suspect that EBD is really just an enhancement to the ABS system.
In the future, there will likely be new "programs" for the ABS mechanisms that go even further to control nuances of the braking force. Just like the way the throttle pedal is now just sending a signal to and ECU to suggest how much air/fuel to give to the engine, the brake pedal is starting to just be a signal indicator that various ECUs will use as one input to control the braking. We ~are~ losing control, but in many ways the "drive by wire" system is superior. One example - Mercedes is testing a "virtual" crumple zone which is basically automatic braking if sensors detect that you are just about to run into something.
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