The DF-15B has similar or better performance than the Iskander which is allegedly the basis for Kinzhal.
The DF-15B has similar payload but much longer range. The last stage at least looks similar to the one in the photo.
I think it is highly likely the Chinese used the same concept and repurposed a similar missile.
But the DF-15B is a lot heavier than the Iskander so I wouldn't be surprised if they had to change a lot of things in the design.
The fins could have been removed or redesigned. An air launched missile will have a different flight profile than a ground launched missile too.
This is speculative but the low resolution quality of the picture doesn't give much room to positively identify it.
Still great find, first time we see the much rumored large missile variant in captive carry on an H-6.