Good definition of the character arc. Is it possible that a character who remains steadfast at the moment of climax undergoes the transformation of realization?
To which I replied:
In regards to the question about the "character that undergoes the transformation of realization" it depends on what you mean by realization. If you mean a realization followed by a change in approach then no, that would apply to a Changed Main Character.
If instead you mean to say the Main Character comes to a point of realization as to what has been driving them and must then decide to either Change their approach or Remain Steadfast then yes, this applies to the Main Character.
One of the purposes of narrative is to show us how we can become blinded to our own justifications when it comes time to solve problems. The process of a story tears down those blinders until the Main Character is finally able to see the difference between their real problem and what they thought was their problem. Until that moment of climax Main Characters simply address the Symptoms of their problems, rather than what really drives them to do the things they do. That moment of realization the reader refers to could be that moment when the Main Character decides one way or the other: continue responding to the symptoms and renew his or her resolve (Steadfast), or address the Problem directly and try something new (Changed).