Any issues using PAEMPPOS table to evaluate FTE?

I am testing a new eligibility file that will be going to a vendor. We are required to send current employees who are eligible, employees who were eligible but are now ineligible because of a status change (old FTE>=.40 and newFTE<.40), or they termed in our system. The ineligible employees only need to pass on the file once.
Below is the criteria in a crystal report I put together (EMPLOYEE table has an outer join with PAEMPPOS so you can get the previous FTE on PAEMPPOS) to test the file. Our programmer is using PERSACTHST and is looking at reason codes to determine when an employee has lost eligibility and action code to determine when to send terms. The issue with this is:
1. They are missing employees who are keyed with a different reason code than what's hard coded and their FTE really did change;
2. They are showing employees on the file that had an FTE change BUT they were never eligible in the first place. EX: oldFTE .30 and newFTE .10.

I asked about using PAEMPPOS to evaluate this and all I get from any of the programmers is, "We don't write eligibility files that way. We've never done it that way." Okay, is there a reason why we haven't done it this way because it seems pretty accurate so far.

Eligible employees
{EMPLOYEE.EMP_STATUS}in["A","L"]AND
{EMPLOYEE.FTE_TOTAL}>=.40 OR

 

Employees who have lost eligibility in the past 7 days due to status change
{PAEMPPOS.DATE_STAMP}IN {?Date_Report}TO {?Date_Report}-6 AND
{PAEMPPOS.FTE} >= 0.4 and
{EMPLOYEE.FTE_TOTAL}< 0.4 and
{EMPLOYEE.FTE_TOTAL}<>{PAEMPPOS.FTE} OR

 

Employees who have termed in the last 7 days
{EMPLOYEE.EMP_STATUS} IN ["U","TP"] and
{EMPLOYEE.NBR_FTE} >=.40 and
{PAEMPPOS.DATE_STAMP} IN {?Date_Report}TO {?Date_Report}-6

Can anyone give me some good reasons why we wouldn't want to evaluate off of FTE in the PAEMPPOS table?

Thank you,

Sarah