Correct, in order to get a pakistani (or ANY astronaut of that matter) to do a short stay you MUST do the endurance test. China will not waste an empty space on upflight or downflight.Now come to think about it. Is this endurance test corelated to the Pakistan astronaut joining? One crew member staying for two "tours" would mean now there's an round trip empty seat. Then they decide not to waste it by taking a foreign astronaut for a one week experience on the station.
Personally, this means we will very likely see the female arm of the endurance test done with another foreign astronaut (my bet is on Russia, Brazil, or Thailand).
Once tiangong expands an additional 3 modules there may be more flexibility for short term stays with more docking ports, but right now they will likely keep with the 180 day mission tempo to efficiently maintain continuous presence on tiangong.


