There's a misunderstanding in the designations, it seems. The recent photo of the "J-10C" prototype not only suggests that none of the rumored improvements were made, but that the entire J-10B program had gone backwards by removing some of the J-10B's features.
However, that is unlikely to have happened.
Instead, a plausible explanation would be that the photo of the "J-10C" is either that of a "J-10C" subsystems testbed or an export variant of the J-10B for Pakistan. The real J-10C, which will include "comprehensive upgrade" that will certainly alter its appearance, is not revealed yet. A strike fighter, as is rumored to be the J-10C's role, would require twin seats as well as an upgraded engine which would dramatically change its physical configuration. The J-10C would still have upgrades like twin seats, upgraded engine, new radar, conformal fuel tanks, and such.
It's just that the current photo is not of a J-10C but rather some other unit.