As far as I know and can reconstruct from the S-89's I worked on over time, the distinction between 1st and 2nd RV got lost as per that 11/20 version, 2 years ago. This is when the name of the 4up changed from having Mu to having Mlt in it. As per the jan 21 workbook, you don't find 1st RV anymore.
I think behind the scenes TB just inactivated 2nd and 3rd RV, but 'return visit' is still called '1st return visit' behind the scenes and this '1st return visit' shows up as programme part on the assignment if you use the 'copy assignment' button to text the student. This is confusing if there are 2 return visits, since they would both be called 1st return visit.