I didn't even notice the ground edge of those teeth in the photo. I was just looking at the normal wear of the teeth like you can see in Rob Farmer's Photo. Rob's photo is a good photo of what to look for. I suspect RD's teeth are ground that way because the sprocket wasn't fully installed on the crankshaft and the resulting chain misalignment caused the sprocket wear. I have had sprockets stick before they are all the way back but I fix it! I always make sure the sprocket hits the back of the crankshaft and STAYS there until it cools. I also make sure the tips of the sprocket teeth do not discolor from heating it up thusly ruining the temper.
RD, you just need to replace the crankshaft sprocket. It looks like it isn't on all the way anyway.
Duplex versus simplex? The duplex chains wear faster as well. Why? They are a lot heavier and a lot more complex in both their machining and how they are SUPPOSE to work. Each roller is suppose to share the load equally. I doubt that happens much either for the sprocket's machining or the sprocket's wear or a combination of both.