Although muscles have 'fibres' it's just another medical term to describe muscle 'cells'. Bottom line is with today's Pros and insulin abuse, it has a huge effect on how the cells appear, even when the body is 'dry' and lots of diuretics are used the guys who have been smashing insulin year round, the muscle cells are going to become smoother as they're holding more nutrients/liquid.
Wouldn't matter if they followed munzer's conditioning protocol or hardening compounds to the tee, their muscle cells are smoother - you can't change that look no matter how much subcutaneous fat & water you lose....