I am not in the area but Xiaoou is not nobody in the area. He used to work (or visit) at MS Research Asia and Chinese Academy of Sciences. He had best paper awa

I am not in the area but Xiaoou is not nobody in the area. He used to work (or visit) at MS Research Asia and Chinese Academy of Sciences. He had best paper award from CVPR and served as chair of ICCV. That all being said, we all know how research goes... I am just curious why they put it on arxiv. Is this a common practice in the CV area or is it because someone else is working on a similar approach?