When the mutant in the protective suit comes through the door, he supposedly has been completely transformed from human. The green mutant make-up on his hands and wrists ends and the audience can see his normal human skin under the sleeves of his suit.
The mutant could easily bend the jail bars to enter the doctor's cell, but when the doctor locked the mutant into his cell, the mutant seemed unable or uninterested to bend bars again to chase after the doc.