[whpalmer4]

You are looking at a project view, where the sorting unit is projects. If you want to view a sorted list of actions, do it in context mode, where the sorting unit is individual actions. The fact that there may be a very recently completed action in a project matters not at all for the sorting of the projects, unless completing that action completed that project.

In both views, with all else being equal, the items appear in the order they appear in the sidebar. If you look at project view, sorted by completion, and none of the projects are completed, the first project shown will be the first one in the sidebar, for example.

So, if you want a list of all of your completed actions, sorted by when you completed them go to context mode, group by completion date (or ungrouped), sort by completion date, show completed actions, any flag state, any duration, and you should get what you want. If what you want is a list of incomplete projects, sorted by when you last completed something in the project, you may be out of luck, as OmniFocus isn't really set up to do that sort of thing.