There are a few small gaps in the thick rail blocks but every single pan bolt is "anchored" to a main bulk head. Every main bulk head has some connection to the thicker part of the rail anchoring them to more meat. This should also keep the entire block from flexing as much in extreme builds and make bore last longer even though they may be a little thinner.

Also I am not a metallurgist but I can tell you the magnum block metal seems quite a bit harder when grinding for stroker clearance.