I think it's important to remember perspective... They're marketing them as underwear, and shots like that are fairly typical in underwear marketing (much more so for adult underwear, but it's still not uncommon for youth products), so it helps to reinforce the notion that they're just like underwear, by similarly implying there's nothing unusual about pictures of them. Doing shots like that keeps it in line with their ever-present marketing campaign about how much they resemble normal underwear.
It's also worth noting that, folded up, as they are fresh out of the package, they're very clearly a diaper of some sort. The rectangular shape of the pad is glaringly obvious. They don't really begin to lose any of that diaper appearance and really look like underwear until they're being worn, and conforming to the shape of a person's body. As an example, if you go look at the product pages for GoodNites on Target's website, they have GoodNites folded up in dresser or nightstand drawers (they did some odd things on those product shots...the prints on some of the GoodNites are simulated, while others are real; I suspect they may have changed the prints after doing the photo shoot), and...they're very obviously a diaper (let's not get into the debate on what is and isn't a diaper right now). It ends up running counter to the goal of trying to promote them as underwear, even when presented in an underwear drawer. It just looks like diapers in an underwear drawer. Those images also include kids wearing the GoodNites, and from a marketing perspective, it works a lot better than the shots of GoodNites in a drawer.
Close-ups of what's basically a diaper, actively being worn, may be a bit distasteful, but they're also not unusual for baby diaper marketing, nor for training pant marketing. The kids wearing them are certainly at an age where privacy and modesty are more of a social norm, but...welcome to marketing. It's always trying to push boundaries, and especially in a context where they're trying to normalize older kids wearing what are, effectively, diapers, they want to push those boundaries as much as possible. It's the only way to accomplish that goal.
Speaking of DryNites... Those shots highlights an odd design element... I think it's showed up on Pull-Ups New Leaf in the US, as well. All the boys versions (well, not the smallest DryNites size) have a printed tab with buttons in the front, at the waistband. Does anyone know what that's even supposed to represent? I've never seen that on real underwear, and the only things I can think of for practical uses of such a design on real underwear are for tethering the underwear to either a shirt (keep your shirt from riding up) or pants (your underwear automatically goes up and down with your pants), or for holding a pocket closed, that would contain an absorbent insert on reusable training pants (which would be a really odd thing to include on the DryNites, and even on Pull-Ups, since they're supposed to look like regular, non-absorbent underwear). Unless it's some unusual sort of fly, where the entire front folds down, like the opposite of a butt flap on pajamas? The ones with the buttoned tab are missing the usual fly, and indeed, the smallest DryNites, that lack that buttoned tab, have a traditional fly...
