I think you accurately are describing backcountry backpacking where you start at a trailhead, determine where you will camp, how many miles to cover, etc.
I believe from the stated story that he was planning to be walking on scenic byroads (it said he's avoiding highways and main roads) as opposed to a trail. That allows him to buy things along the way, occasionally hitchhike or ask for a place to crash, etc. There is plenty of national forest out there where he could also pitch a small tent near a road, crash and then keep moving in the morning.
If he was following roads, then the long time staying out of touch makes even less sense except that as a young man out on the road, he likely didn't want to feel obligated to call in (a la Jack Kerouac).
As others have pointed out, this is a very cold time of year to be attempting this and I fear that with little to no information on his planned route, it will be challenging to find him. I am still hoping he just was enjoying the freedom of being "out there" and decided against checking in. Hopefully someone recognizes him and can let him know he is missed!