I can relate to this. These days, I see a lot more city trees than ancient mountain trees, and I absolutely have bonsai that will more closely resemble city trees than mountain ones when they're in their final forms. Various forms of broom style tree are ubiquitous in the city, and there are some very interesting ones around that I'd be happy to own in miniature. Plenty of inspiration to be found.
For me, saying this is not natural is confusing. The tree's response to whatever stresses, constraints or abuse it's had is 100% natural, and when a tree is left to it's own devices to recover after whatever's been done to it, the damage blends in organically, and just becomes a feature on the tree that adds to its character. It is simply a reflection of the environment it was growing in.
I mean, I get it. You're probably going for trees that look untouched by humans, and those can be truly astounding specimens. But I think that's going to be a very subjective preference depending on who you ask. For me, the beauty lies in the tree's underlying system, and how it responds so beautifully to adversity. When thinking about it this way, I find the origin of the adversity becomes less relevant after a while.
If you really want to go down the philosophical rat hole, I could easily argue that we, as natural beings, are as much a part of nature as the tree, and therefore, it's all just nature anyway (and therefore, all natural). But I could just as easily argue the opposite, so I won't do either.
I'll instead leave it as simply a subjective preference of one form over another. =)
Cheers