I've heard of that old design with ramped pistons and I've seen diagrams before, but I didn't know it was ever used in RC engines. Pics?

I have 6 different types of engines in my fleet, and only one of them has a lip under the exhaust port. That's why it seems so odd to me. It honestly looks more like the sleeve is just being used in an engine with longer stroke than the sleeve was originally designed for.