its not flattened out. its called a vaccuum, something that dexter's alien turtle gut and fucked up torso would never allow him to hit.. 
dex couldn't touch this in a million years: 
you must be so dumb as to think i dont know what a vacuum is.
to make my point clearer for you....ill spell it out..
when shawn hits the FDB his chest flattens out, his arms spread and the peak in his other poses disappears markedly. Additionally he appears smooth and his lats all but disappear also.
then his big blocky legs jut out like pylons without any real flair or appeal.
ever wonderedd why he does a vacuum and no one else does?- its because thats the only way he looks half decent in that pose. Without the vacuum his flaws are more apparent.
would you like some more BB 101 schooling?
i see that despite MW and ND and myself serving it you still seem to be having a hard time grappling with it.
PM me if you'd like some tips and hints. I'm happy to help.