Turns out that it was a picture I saved on my hard drive. And it said 'Fanart_by/Luuluu', which I'm sure I saved a long while ago. That is where the misunderstanding comes from. It's because I had this for such a long while, and I see it freshly on Dev art while I had it all this time. I thought it was suspicious. But no, it was not concept art, it was the same picture here. So my apologies, it was just a misunderstanding.