I don't think it runs fluid around the thrust piece/preload. It's mostly grease around rack and pinion. In the photo below, around the red box is where fluid runs and blue box has grease (the reason I say that is, once inner tie rod is removed and wheel is turned all the way to driver side, i can see the rack groves on the shaft, if there was any fluid it would be fluid bath).
Inside the thrust piece/preload, there's a piece that holds/keeps load on the shaft and a preload spring and rubber cap on the thrust cap.
This is what's used in ThyssenKrupp unit, left is renewed version and right is old one.