I compare J-31 (KSA interest) to the JF-17 stage before Pakistan committed to the project decades ago. JF-17 did not have either cases before that stage either. JF-17 could have went nowhere like where it is today just like J-31 may go nowhere.You made my point on the JF-17, because it had a partner providing both some funding for development and demand for the finished product from the PAF. Neither case is true for the J-31.
What I was trying to say is that KSA (if the rumor is to be trusted) is building that case for J-31 just like Pakistan was building that case for JF-17 in the past.