If you had noticed the difference in between landing speeds of Mirages, F-7s and JF-17s, you will have your answer as which is more demanding for such operations.....the issue with JF-17 is same as F-16....it's intakes are again much lower than say Mirage, again the issue of FOD.....If PAF can fly it's F-16s to say Turkey and UAE, not sure why would there be any issues with them operating within the country.There could be many reasons for JF-17 such as its ability to perform this operation at the moment or PAF's willingness to do it, as they don't want it to get involved in any incident that may impact its reputation. Also, the event is being covered by the media so any incident involving JFT would be seen worldwide, remember the humiliation IAF faced a few years back when they landed the jets on the road after multiple approaches. How many times have you seen K-8 or Mushak landing on the road, once or twice ? JFT will take time to do so.
But for F-16 the reason is quite obvious.