So does the official rate. The U6 adds in people who aren't trying to work (but might start looking soon) and people who are working, but not enough hours. And since the only difference between the U5 and U6 is the part time for economic reasons, it's kind of dishonest to not mention that it includes people who have e steady jobs.
This is what the U6 number is according to the Dept of Labor.
The six state measures are based on the same definitions as those published for the United States:
U-1, persons unemployed 15 weeks or longer, as a percent of the civilian labor force;
U-2, job losers and persons who completed temporary jobs, as a percent of the civilian labor force;
U-3, total unemployed, as a percent of the civilian labor force (this is the definition used for the official unemployment rate);
U-4, total unemployed plus discouraged workers, as a percent of the civilian labor force plus discouraged workers;
U-5, total unemployed, plus discouraged workers, plus all other marginally attached workers, as a percent of the civilian labor force plus all marginally attached workers; and
U-6, total unemployed, plus all marginally attached workers, plus total employed part time for economic reasons, as a percent of the civilian force plus all marginally attached workers.