We did it in Nov. last year. Nov. 10th to be exact. Not sure why that CM told you that.

Maybe they weren't doing it then, the CM was mistaken, or we were lucky and they had reinstated it before we asked.
I had never asked to do this before but after reading about it on there boards (along with riding in the engine on the train-did that, and riding in the Lilly Belle-haven't done that yet). DD10 and I went for a short visit after school that day and as we were walking by the Mark Twain she mentioned she wanted to ride. I remembered what I had read about riding in the wheelhouse and told her we should give it a try. I asked the first CM we saw on the dock and he turned out to be the pilot. He took us right up there (we got to board first, through gate to the side) and told DD when to pull the whistle and ring the bell. It was pretty fun! The wheelhouse is pretty small so I'm sure there's a small limit on how many riders they can accommodate. With the 3 of us (Pilot, DD, and me) we were pretty much at capacity.
DD and pilot.
In the pictures it looks like it was really dark out but it was just at sunset. Which made for a beautiful ride.