To the best of our knowledge, there is nothing to indicate a structural change in EMPSTAT implementation in 2001. The uncollapsed labor force fields (i.e. NILF, retired, NILF other, etc.) were new in 1994. Furthermore, as you can see in the 2000 and 2001 CPS codebooks, the categorical options for PEMLR and A-LFSR remain the same for both 2000 and 2001.
Finally, in looking at several CPS interview manuals, it appears that someone is identified as retired if and only if any of the following is true: a person says they are retired from work, whether voluntarily or not; a person says they retired because of health; or a person says they are “too old to work any more”.