Like you, I don't like that the stimulus for displaying things in the file pane is different either, but alas we seem to be stuck with this behavior. There's virtually no configurability in the way Explorer interacts.
You can hit return on the folder to make it show in the right pane, then continue moving around the navigation pane with the arrow keys. Space bar works too, but it goes "ding". This is not as efficient as just moving the highlight around used to be.
FYI, the Explorer changes has indirectly and adversely affected how the mouse scroll wheel works, too. Now, unless one installs a 3rd party app to redirect mouse events, it almost ALWAYS seems like the mouse wheel scrolls exactly the wrong window. Fortunately there's a feeware app out there that helps a lot with that: Wizmouse.
-Noel