I just tested this mod, and it absolutely takes away more force feedback effect than just the FF letting up or going light when the car understeers. It is completely obvious and anyone who took 5 minutes to test it would come to the same conclusion.
It also reduces some of the build-up of FF when going into a corner while you still have traction.
I'm not sure if this mod was tested by the uploader, or just a copy/paste from a 2012 mod or what, but that's what I just found out testing back to back files.
I will do further testing and I think I can accomplish what this mod tries to, but with more of a scalpel, instead of a sledge hammer.
I will actually test it thoroughly before making claims of what it does or does not do.
****EDIT****
With 10 minutes testing I was able get rid of that understeer FF let-off.
Change this
<FFBSlipAngle scale="1" min="0" peak="0.41" max="1.08" forceThresholdLow="0" forceThresholdHigh="115" minForce="2.5" peakForce="10.0" maxForce="0.38" scaleThresholdLow="0" scaleThresholdHigh="90" minScale="3.5" peakScale="6" maxScale="1"/>
To this
<FFBSlipAngle scale="1" min="0" peak="0.41" max="1.08" forceThresholdLow="0" forceThresholdHigh="115" minForce="2.5" peakForce="10.0" maxForce="6" scaleThresholdLow="0" scaleThresholdHigh="90" minScale="3.5" peakScale="6" maxScale="1"/>
See it makes perfect sense too.
maxForce = force for all linear forces when slip angle is on or above max /
That was the first value I tried, and it worked fine. I suppose you could fine tune that, so if you wanted a little bit of that effect, maybe try a 1, 2, or 3, or if you wanted the FF to continue to build, maybe 8, or 9, or even 10.
6 was a guess and it seems to work great without affecting any of the other FF effects that actually help you feel what the car is doing. I might try different values to see what it feels like.
Try the stock file, and my change and the one in the OP back to back if you want to see the difference.