Most numerology traditions distinguish the destiny number from the life path number by what each is supposedly "about." The life path, drawn from your birthday, is framed as the terrain you were born to navigate. The destiny number, drawn from your name, is framed as the toolkit you were given for the job.
That distinction is tidy — maybe too tidy. It's the kind of clean division that makes for a good chapter structure in a numerology book, whether or not it holds up to scrutiny. Worth noticing, not necessarily worth trusting.