While of course there's a lot of commonality, not all thru-hikers do their hikes the same way or focus on the same things. I've met people with a couple of hundred miles to go who just hated it but were gutting it out so that they didn't have to say that they quit. Last year on an October trip I met sort of the laggards, and it was a bit odd for me --- they seemed sort of like 'my tribe' but sort of not, too. An eclectic bunch in their own right with various reasons why they were still on trail in October.

Food certainly does become an obsession. It's just "part of it", though, and I don't think that makes it any less 'backpacking'. Doing the miles is just something you have to do, it's background. In fact, I've rarely been on any sort of backpacking trip where folks weren't aware of how much mileage they have to do for their alloted trip time. Thru-hikers just can and do more per day on average. I certainly agree that if it gets to be *just* about the miles, it's not like more typical backpacking.

Rather than say "thru-hiking is not backpacking", I'd suggest instead a broader definition of backpacking that includes many style variants. An overnight trip with kids is quite different than a week-long trip with a group of fit and experienced friends, but both are backpacking. Base-camping and doing a series of day-hikes from the basecamp is different than doing a long loop hike. Etc.

Doing long distance trips has changed my default way (personal style) of backpacking; much of the approach used for longer trips I retain from habit and preference now on short trips. I really do think that "it's all good".

If you ever do the PCT, I suggest a sort of 'third way', what some now call Chunk hiking. More than a section at a time, less than a thru. That way (if you have the time of course), you reap the benefit of getting into shape and up to speed in a way that section hikers don't, yet you're not setting aside months and months at a time. Also, travel logistics are less of a hit on a per-mile-hiked basis.

Section hikers are always dealing with a lot of travel and other logistic issues, and are always "just getting back up to speed" (often both mentally and physically). It's hard to express how great it is to get fully ramped up and strong and then still have a lot of miles yet to walk to be able to really enjoy that.