The title is a leftover from the book. In the book, when they got married, Jamie was much sicker than she appeared in the movie (in fact an earlier cut of the film had her practically at death’s door when she got married).
In that version, she was wheelchair ridden and they did not know if she would be able to walk down the isle or not. She did and Landon thought “It was the most difficult walk that anyone had ever had to make. In every way, a walk to remember.”
The film-makers tried to explain this — with mixed success– by adding the bit of narration from Landon about “the visions of Jamie walking toward me will stay with me forever.”