If you take a moment to look at the section Path Project/At a Glance, you'll see in there that they don't claim to provide all of their own food, and at best only 80%-90% in the summer. Also, at several points in the site they mention the fact that since they decided to make money on some of what they produce, they've gone boutique in some ways. This means growing more garnishes and spices rather than sustenance plants so, the percentage of what they provide for themselves may have even gone down since that post.

Also, you are correct about the main part of the site not being updated in more than a year. However, if you take a look at the Journal Section there you'll see that the site appears to have taken a turn for more of a Blog type page and is very active. There were 5 posts on leap-day alone including an interesting look into the family's diet for a week. As with Blogs, some posts are fluffy filler, but others have some great info in them.