"Specifically, to be counted as marginally attached to the labor force, they must indicate that they currently want a job, have looked for work in the last 12 months (or since they last worked if they worked within the last 12 months), and are available for work."
Yes. Where in there does it say anything about excluding people who haven't worked in 12 months? Nowhere. The criteria are: (a) Want a job; (b) Available to work; (c) Have looked for work in the last 12 months.
(NB: they also have to have *not* looked in the past 4 weeks or they'd be unemployed under the regular definition. But that's not a criteria for attachment to the labor force, it's a criteria for being *only* marginally attached.)
Now, those people *are* excluded from labor force participation, *as I said*, because labor force participation is based on U3 unemployment, and U3 excludes marginally attached workers. But U4 counts some of them and U5-U6 count all of them.
"if someone has been looking for work but CAN'T find within a 12 month period, they're considered NOT a part of the labor force, and thus not unemployed."
Wrong. Here is the definition of unemployment: "People are classified as unemployed if they do not have a job, have actively looked for work in the prior 4 weeks, and are currently available for work." Nowhere is length of joblessness implicated.
In fact, one of the examples given on the website is of "experienced workers looking for jobs after an absence from the labor force (for example, stay-at-home parents who return to the labor force after their children have entered school)." How the fuck are these people supposed to count if 1 year of joblessness is disqualifying? Did Obama extend pre-K to 8-month-old babies and no one noticed?
You haven't found a single source for your claim that 1 year of joblessness is disqualifying, and you won't, because it isn't.