Here is the best quote from that link:
"Don't be fooled, though, as some dual exhaust systems are actually single exhaust, as a few manufacturers use just one manifold and split the exhaust pipe after the muffler. From behind the car you see two tailpipes, but if you follow them forward, you'll find just one pipe and one manifold. There is no horsepower advantage to a system like this."
THAT describes the Forester's dual system. It's more expensive than a single exhaust, and adds no power. So, it was apparently determined to be esthetically pleasing, perhaps using cues from the "balanced" handling marketing ideas, and, someone finally decided it wasn't worth it to put this faux-dual system on any more.
The Forester's dual exhaust is a fake??? How sad. If an engine has 5 or less cylinders or an I6, it should be single exhaust. A vehicle with a V6 or has 8 or more cylinders, it should be a 'true' dual exhaust with an 'X' pipe. Anything turbo should have 1. But should a manufacturer put a dual exhaust on, it should at least be functional and not a fake. /End rant.