In the flags interface, as this question and its answer indicate, it is possible to view the full post by clicking on the drop-down arrow.
In the /review interface, it is possible to view the full post by clicking on the "review question" or "review answer" link, which reveals the full post.
It seems strange to me that these two tools do the same thing in two different ways. Additionally, I think the folding interface used by the /review tools is preferable, for the following reasons:
It is more in keeping with the current design of the main site, since it works in basically the same way as comment folding.
It is more intuitive, because as you skim flagged answers and see one you want to examine in more detail, your eye is already at the bottom of that post. It takes just a fraction of a second more time to find the arrow and mouse to it than it would to mouse to the end of the post preview.
It is less ambiguous. It's not immediately obvious (to me) what the drop-down arrow above does if you click on it. On the other hand, the "review answer" links follow a simple "click on me to do what I say" idiom.
Would it make sense to modify the flags interface to use folding? A link that says "review post" or simply "view post" would probably be fine. Other options: "view full post", "view question" and "view answer", "view full answer", and so on. Something like this:
The main downside I see is that it makes the flags interface less compact. That doesn't bother me; but then, it may be that diamond mods see the same thing, and need a compact view.