The SD 90's had those steering trucks - and did a nice job of tearing up track. Axle loading is one thing, You still concentrate half the the locomotive's weight in the distance of 1/2 a stick of rail. The SD90's would flex the rail and drop a wheel into the gauge for a brief period, then the wheel would pop back up on top of the rail, the only evidence being the scar on the wheel rim.
That hill has a lot of badly curve worn 90 and 110 jointed rail. On many curves the rail is head is worn to the point where the flanges are hitting the joint bars. The UP knew that when they sold the line off.