They did have power reverse. I have a couple photos to illustrate this, one is a cab shot from loggerhogger's collection in which the mini Johnson bar is present. Also a couple photos in which the power reverse cylinder is visible just in front of the engineers side of the cab. If I get time I could post these later ones. As to the throttle, I think the story is that the original dome and throttle placement proved to be a problem on the very steep grades encountered on the Uintah being too far back on the boiler. To solve the problem new domes were installed on the boilers farther forward and the throttle moved. The rear domes then just became convenient points to enter the boiler.