Yes, they are somewhat banana shaped, but so are the regular ABE arms, The late B arms are not as tall compared to ABE arms, so the curve apears more pronounced.
Over all, I'd say they are probably an inch longer, but the layout makes them look bigger and combined with their flatter layout and increased width, they "look" huge.
I don't have any late B plates left anymore, so I pulled these from the ARE website. This is the regular ABE body brace plate that is about 10" long, 3" wide.
This is the late B plate that mounts up in the same manner. IIRC, it was over a foot long, possible 13". The narrow end is comparable to the early style plate attached above.