Interesting thread, I think I will toss in my 2 cents....
I've driven only a handful of cars in my life, and I'd like to think I know a thing or two about the dynamics of understeer and oversteer, and possibly how they apply to LFS.
I've found that the amount the wheel loosens up when understeering varies car to car slightly. There's still a definite FEELING to it, almost as though you've just driven over something slippery. The amount of bucking the wheel does is extremely dependent on the road surface, of which LFS's is utterly flat for the sake of argument.
I think everyone will agree that when you're understeering, your front wheels are not rotating at the rate which the road is passing under you... on top of that the road is not moving paralell to the wheel's preferred axis of travel. This means that a small perpendicular force is being applied to the side of the wheel, while at the same time, the usual forces that apply on the axis of travel are reduced (which is what causes that loose feeling).
Depending on the weight of the car, the amount of weight transfer during understeering, and more importantly the inclination on the steering assembly on the actual wheels, more or less of that force is translated to the wheel. An inclination perfectly centered on the wheel, you will feel very little, but an inclination slightly off-centre (normal for sports cars) will translate more of that perpendicular force caused by sliding the fronts to the steering column.
Now that we've lost the ability to adjust the inclination value for the cars, it's hard to test to see if this would give us more or less feel. I've found that in S1 that different inclinations send more or less road forces to the wheel. Driving in the dirt with higher inclination would give me sore arms sending the RB4 through the rally courses.
In real life, I'll equate this to driving my mom's old Pontiac Sunbird vs her Pontiac Grand Am. The Sunbird was a smaller car, but fairly heavy, and had a very tight steering column. Road forces were translated relatively well to the steering column, despite the power steering and everything. When I'd understeer (usually in the rain or snow) the steering column would loosen slightly, but it was still tight enough as the wheels were still trying to follow the road as much as possible. The Grand Am, on the other hand, is a larger heavy car with a little more power, but is much easier ride in terms of the steering column. I've found that understeering this car made a larger difference, possibly due to a different inclination on the steering assembly (possibly something else), where the wheel turns to nothing and it feels like I'm in mid-air (kinda scary the first time it happens).
So it's my humble opinion that the understeer feedback (or lack of force on the wheel, rather) is due to the static inclination set per car.
Personally, in LFS, when I'm sliding under coasting, I can feel the wheels slowly start to regain grip as it slows down, and this is how I can gauge when I can snap the wheel back into place. I've got a DFP running in 900 degree mode, and even then it's quite a quick ramp-up to full grip, so it's possible that on the MOMO's with a much smaller lock, that you're hardly even feeling it. And if you're going straight and you turn to lock instantly at 120mph, you're just going to have a wicked perpendicular force on the sides of the wheels... even at only 30 degrees lock, it's a much higher force than any lack of grip on the preferred axis of travel for the wheel, so don't be surprised if it doesn't go 'light' because the sidewalls are getting the workout of their life and all that perpendicular force is getting sent to the steering column.
That's my best diagnosis