I don't get GAdv.'s excuse "lack of employment". They've said that for pretty much every ride they've removed.
-Tatum "Heck Time Warp's still in the boneyard!"
AstroWorld's Free Fall didn't last very long (14 years) compared to the others.
-Tatum
EDIT: From Six Flags Houston.com
Here's a possible explanation to why it lists SFMidAm as a Free Fall home: