Since Players had only reached the fourth Ruin City, the System had set the Player's max level at 50. Unfortunately, that meant that people couldn't Evolve their Class since one needed to be at level 58-60 tops.
Actually, floors 50 to 54 were supposed to be transition levels for people to get a feeling of what an Evolved class would offer them. But, of course, the classes or skills that monsters earned weren't comparable to what Players would earn, as in most cases, they would be either watered-down versions or unavailable.
In the end, though, those were enough to help at least the expert players make their progress a bit faster.
Ameanum was the first and only Player with an Evolved Class because of a loophole he had found.