What it seems like is this is solely to see if you would "survive" via a TDY.
I just an hour ago finished visiting the Pararescue-CRO school, Kirtland AFB. The cross train applicant assessment is not an assessment to see if one will survive the PJ Development and PJ Indoc course. It exists to assess the applicant does meet PAST and other entry classification performance standards. Getting an assessment go to proceed to the development course doesn't give an assurance of surviving (getting successfully through Dev and Indoc courses) in the way you are most likely are thinking it does.
The PJ cross train applicant assessment came into being needed in technically (an exaggeration) under recently implemented policy everybody in the Security Forces career field could submit an application to retrain into Pararescue and flood the required courses with more students than the Air Force needs and more students than the courses have instructors and facility resources to properly train.
Also as previously disclosed unit commander recommendations, EPRs, and unit certified PAST accomplishments lack accurate (are unreliable and not dependable) in documenting applicants actual current level of performance and performance potential.