I think its just a matter of your personal goals…Even though this is set up with a learning path, its still self guided and its up to you which section to work in and how much of it to do. If you already know all the material and only interested in the projects to have something for your portfolio, then just do the projects, I see no harm in that.
As for going for the FCC certification, personally, I see it as a personal milestone, like ksjazz said… Im not under any impression its what will help me get a job. To me, the certificate will be a representation of my.personal sense of accomplishment and fuel my confidence. Im not chasing the certificate, Im chasing the knowledge I have t gain by completing the course.