Less than 1% change in brightness between 12.5% APL and 87.5% APL is tolerated for a broadcast monitor. Being generous, it looks like a 25% drop in brightness with the KRP.
An LCD, LED backlit or not, maintains brightness at the same level regardless of APL.
The only time where this behaviour is "advantageous" is when you improperly set up your display to 500nt for peak white and try to watch it in anything but a sun-filled room... as APDC set up their test.
And for what it's worth, if you want
that behaviour from the display, though I can't see why anyone would, it is an option on many LCDs now. "Auto Light Limiter" on the HX900, though I have no idea how aggressive it is, as there is no reason to use it.
You will also find that APDC created a "standardised" MPRT test that was specifically tuned so that motion in the test was as fast as a plasma could handle and still score top marks, with LCDs falling behind. (this was back when 60Hz was the only option for LCD and they were essentially capped at 300 lines or whatever it was) Then last year when Panasonic actually did something about improving the motion handling of their displays with new phosphors, they decided to increase the speed to a level which showed the new displays resolving 1080 lines again, with the older "1080" displays now scoring lower on the test.
Sure, it's nice to see that things are improving, but it's intentionally misleading to tailor the test specifically to the displays that you are wanting to show in a good light.
And with them only measuring PDP/LCD displays, there's really no useful information coming out of the tests. OK, plasma may have measured better than LCD in those tests (it would be interesting to see what a high refresh rate, backlight scanning LCD scores now...) but how does that compare to CRT? What about DLP even?