If you plan your story, then you know what your antagonist's fatal weakness is going to be from the outset and you drop clues
And subconciously, you telegraph the ending.

Complete agreement that Davies writes as if he's got his brain in a blender, and his miracle endings don't scan. But I wouldn't blame lack of planning as much as lack of talent. I know many fine writers (and story tellers) who can weave a formidable tale off the tops of their heads.