This is lifted from the original posted article:
In October, the nation’s civilian noninstitutionalized population, consisting of all people age 16 or older who were not in the military or an institution, reached 255,766,000. Of those, 160,381,000 participated in the labor force by either holding a job or actively seeking one.
This suggests retirees are included in the denominator but not the numerator.
If true, this 'participation rate' is a false statistic as a retiree should be in neither one.
Retirees are part of the population, as are stay at home moms, the homeless, people who inherited so much they don't have to work, 20-somethings living in mom's basement, etc.
The LFPR measures what portion of the "adult" population is participating in the LF (working or trying to). LFPR is NOT a measure of the people in the LF who are actually working (roughly the inverse of unemployment).
IMO, it's not a "false" statistic, but a weird one that needs to be taken in context. Viewed w/o context, a low LFPR could mean a society where women don't work or a really great economy where tons of people have retired early or a society of subsistence farmers.