Although the RX-8 doesnt have a "B" beam if you notice its also not a full length 4 door. Its a small front door with a small suicide rear entry door, combined they are about the same length as a traditional coupe door. This car however is a true 4 door sedan which should have the "B" beam.

but dont get me wrong i dont think the vehicule requirs a "b" beam but it does seem to be standard for that design.