New City Being Developed

It's almost as if the artists making this deliberately put the Bastion background as a backlash by confirming it's indeed a rip, then they changed it to correct their "mistake". I don't think anyone is that incompetent to intentionally post content that is clearly not theirs unless they wanted to draw attention to it.

But let me know if they go as far as to make the maps fall into place as you progress.

It's concept art. Artists usually take images as reference to get inspiration, like Bastion in this case. Of course, if you are using those images as original art... Better use images fully created by you.

They most likely forgot they used that image.