Yet another example of inconsistent UI, and once more related to the C-Store.
Perhaps it's an artifact of the way the Nebula was tested - by allowing anyone to pick one up on Tribble, it couldn't be claimed from the C-Store UI.
You'd think these things would be a solved problem by now.
No. Testing has nothing to do with it. As I said above, it has to do with the fact that the Neb can be purchased from the shipyard store for Marks. The process is slowly being changed so that ships get picked up at the shipyard store rather then through the c-store UI as you advance. The Neb is the first. When the Excelsior gets a Marks version it will be added, and so on.