You are quibbling over semantics.
Most people use the word "creationist" to mean someone who believes God created each "kind" of animal seperately. The writer is merely following this linguistic convention.
Thus when the author says he rejects creationism, he is not rejecting the existence of the creator. Rather, he is rejecting special creation view.
Now it is true that there are many who, like me, believe God is the ultimate creator of all things but that he used macroevolution as his means of creation. This view could be considered a "creationism" of sorts, since it affirms a creator. However, the term is not commonly used to describe this view, which is commonly labeled as "theistic evolution." It is the view of the author, BTW.
For the sake of consistency, I think it is prudent to follow linguistic conventions, even if they are not totally logical.
Naw, that is just one view, and not necessarily the prevalent one either. Actually, I don't think that there is a particularly prevalent view amongst creationists on evolution. At one time, creationists enthusiastically embraced evolution - that is until Darwin and his disciples went out of there way to diss them.