No. There was a substantial grousing about this number when Trump or somebody floated it before. The first rebuttal was to conflate his remark with the unemployment figure.
WaPo - Recidivism Watch: Trump campaign on 58 percent of black youths `not working' - Aug. 28, 2016
From your link....
Counting people “not in the labor force” in this 16- to 24-year-old population is especially problematic, because the number of people who aren’t looking for jobs includes people who are in school full-time. Trump essentially equated the employment statuses of, for example, a 16-year-old high school sophomore with a 24-year-old with a master’s degree and looking for a job.
After our fact-check published, Trump and Conway stopped using the term “unemployed.” Instead, they now say the 58 percent figure refers to black youths who are “not working.” It’s a step in the right direction, but it’s still misleading.