Because it's far from new or newly documented. J-10S has been around for many years, and that particular airframe has been photographed and documented since at least 2013. I fail to see why it warrants a post, other than to satisfy a fetish to waste space, which is something he enjoys doing, going so far as to post about a machine gun mount that has been around for more than 13 years and photographed countless times. It might have deserved a post if the image had been high quality and/or aesthetically pleasing, but it wasn't. So the post is an all-round waste of space.
Oh come on ... we have seen several more useless posts including long stupid discussions (just to remind to that stupid one on the Z-19's alleged ATGM just yesterday) and batches of worse, more blurry and dated images than this one. Yes, that particular aircraft is neither a new serial number nor that image the epitome of aviation photography, but it is a recent one, it shows several interesting details including the construction number and if one does not like it, he/she can simply ignore it.
Again, there are pages of useless, political and most controversial stuff here in this forum and you never care, but if he posts an image, you always react like being allergic, IMO it is not worth the mess.
I really don't understand why you are always so much upset?!