Rules Clarifications

Question about Monster Movement

Page 17, Monster Turn Order, 1. Move

"You may move up to the number of footprint spaces indicated on your monster card. In all other aspects, Movement follows the same rules as Adventurer Movement; however movement can not be modified."

The thing I don´t understand is: How can/can´t a monster move and an Adventurer can´t/can - what is the aspect that sets Monster Movement apart?