I didn't say that SOME stiffness wasn't good. But, what YOU said was "thickest sways" front and rear and "highest spring rates".

That's wildly different than just "stiffest rear bar" and "spring rates that are appropriate for the track and to compliment the balance of the car".

To answer your question, a lot of FWD racers will run soft in the front and stiff in the rear because that's what a FWD car needs for balance and to be able to put down power when exiting a turn with minimum inside front wheelspin.

But, again, that's NOT full stiff all around. There's some thought and a lot of testing involved in getting such a setup right.