Yes it would be nice to have previews of everything, but it probably can't be done for everything.
And by that I mean it would be hard to have a preview for something that contains options, like some weapon costume boxes.
Since they have several items inside them and you can't lock it to only show a preview of 1 of them, and having it preview the costume matching your class might be tricky to code.
Same can kind of be said about the apartment styles, how would you preview an apartment style?
Showing the apartment from the outside? Showing a wall from one of the rooms?
Tricky thing to give a preview ingame of.
Pretty sure they mean the ingame preview you can do in the marketplace by shift + clicking or just clicking on things