In order for a solidify feature to remove material the feature used to cut the model has to meet certain conditions it doesn't just simply remove what's to the left or right of the plane. In the case of a cutting plane (datum plane) the plane must intersect (pass through) the feature geometry or model geometry.
In your second picture it's a bit hard to tell what the cutting plane passes through but it looks like it passes through all the parts (pieces). In the third picture the orange wedges in the center, the outer ring, one of the inner grey rings, and two of the wedges between the cylinders have material removed because the cutting plane passes through the geometry, the cutting plane doesn't pass through any of the cylinders. In the fourth picture the same parts (pieces) have the opposite side of the material removed because you changed the side of material removal.
You can see the same behavior in a part. You see it by having the plane pass through the solid geometry, when you move the plane in the direction opposite to the direction the direction arrow for material removal points you should see more of the geometry gets removed from display. When the plane no longer intersects the geometry the entire part gets displayed.
You also see this behavior in a part if geometry regions are not connected. If the plane passes through only one of them, the region the plane passes through will have material removed the other will always display.
I'm not a Simulate user but from the steps I've seen used to prepare models I could see where an assembly cut might cause problems if my assumptions are correct. My assumption is Simulate would want the cut at the part level. Since you are using a pattern of a part you run into problems since you have a part in three states: no removal, partial removal, and complete removal of material. My guess, based on on what I'm seeing, is your original assembly with the hub, outer ring, cylinders and retainers would only end up with the hub and outer ring if the intersected cut was redefined to intersect at the part level.