I'll concede the point that trying to defend a smaller area is obviously easier, but if they're going for ease of defense it still bugs me that the settlers wouldn't have picked an area with better sight lines and features more easily adapted for defenses.
Yeah, if you're going with "but it's easier to defend that small area" argument, why pick the least defendable area to congregate around, instead of, say, the area by the bridge? There at least you have a moat on one side, only one point of entry by the bridge side (any enemy forces has to cross what is basically an irradiated moat which, in the case of humans is not only hazardous but also leaves them vulnerable to weapons fire).
Not to mention this arguement makes very little sense anyway, as it's not that hard to build up a wall around the houses and utilize them as part of it. Plus you have the advantage of having cover to shoot from in the advent of an attack.
It'd be like if Diamond City had said "okay instead of spreading out throughout the whole stadium and utilizing as much of it as possible, we're just going to congregate around 2nd base and build a wall around it"
So here's my whole list of settlements I do and don't use plans for, and which ones I do plan on using plans for.
* Sanctuary: No.
* Red Rocket: No
* Abernanthey: No
* Starlight Drive-in: No (It's one of my biggest cities if not thee biggest)
* Sunset Tidings: No
* Tenpines Bluff: No
* Graygarden: Yes (Although I kinda regret it. Thing is, the plan presumes you want to populate it with people, while I prefer to keep the theme of 99% robots. I have all of one human settler there and all he does is man artillery on the highway.)
* The Mechanist's Lair: No (I use Mechanist Lair's expanded so I make use of the whole lair and turn it into an industrial center. Also, just like Graygarden I like to keep the population 100% robotic)
* Nordhagen: No. I was planning on using Java's plan for it, but it didn't work. So instead I Just built manually. Quite glad I did, it turned out quite nicely I think.
* Warrick: No. I was going to use Java's dock plan, which unlike Nordhagen did work. However, it didn't suit my needs (any plan without plots to put your artillery guns is no good IMO), so I decided to build manually. I did borrow some elements from the plan though.
* Hangman's: Yes, as there's little else to do there. I used Java's version, not the default one. The shops don't really work, but oh well, not like I planned much there anyway. I did cheat a bit though and put some artillery on the roofs once it hit L3.
* Oberland Station: No.
* The Castle: No. I was tempted to do Timkeck's Fort Independance, but decided against it too. I dunno, I might 180 on that, but probably not.
* Country Crossing: No.
* Jamacia Plain: No
* Finch Farm: No
* Greentop Nursery: No
* Outpost Zimonja: No.
* The Slog: No.
* Someville Place: No.
* Egret Tours Marina: No.
Those are the ones I have so far. As for the remaining ones:
* Bunker Hill: Definately. It's not like I can do much else with it anyway.
* Coastal Cottage: Probably. Again, it's not like I can do much with it anyway.
* Covenant: Yes. Again, a settlement I can't do much with.
* Kingsport Lighthouse: Probably not.
* Murkwater: No.
* Taffington Boathouse: I have the Java version, so I'll see how that pans out.
* Custom Settlements: Yes to the ones by Yagisan.