...it was just "one of those things".
Yup. Or a buglet.
Maybe.
The problem is with the highlighting. Note that if an item is control-clicked again (i.e., to deselect it)—and then the list is scrolled—the highlighting is removed. So it must be some sort of refresh glitch.
Another strange behaviour is the case of the single selected item. Normally, the current movie (i.e., the one appearing in the info panel) is also selected in the list. As this illustrates, it doesn't have to be—it can be deselected. But if there are no items selected, the movie appearing in the info panel will always be treated as if it is selected. That is, any operation selected will be performed on it. I'm sure that's by design. And maybe the highlighting glitch is too—so no one will notice the inconsistency.