Why both wheel block and derail?

One of the tracks in GCT (30, I think) has been used for a while to store a work car at the end. The track has both a derail and a wheel block installed (I hope I used those terms correctly). Why both? What does one do that the other doesn't? I've never actually seen the derail used; it's always folded out of the way.

The attached photo was taken on a day when the work car wasn't there. Actually, it seems odd that there's a wheel block facing the empty part of the track, not towards the part that's in service. I don't imagine the rubber traffic cone would do much to arrest the train should it not stop soon enough.

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I believe they use this if private cars are stored , so other trains can still use rest of platform.
It has to do with FRA camp car rules of occupied sleeping cars.

That work ties in with East Side Access. The car was loaded with old elevator gear parts and brought downstairs for unloading in East Side Access construction area. Think a new passageway will end up in that area.

Like Dutch said as per FRA regulations that derail protects against movement.

The cone is holding up the "STOP" sign that should be there.