That's a typical process that companies, who want to sponsor green card to their internal employee, are required to do. They have to find an equally-skilled US citizen by posting jobs publicly for X amount of time. Then after they have collected applications, they "review" and reject them; use that as an evidence in filing the green card for the internal employee.

It is a broken/absurd rule and only puts more work to everyone involved (not just the applicants, the HR; the internal employee and his/her manager, who usually has to get involved in that process). The process itself is also relatively expensive (cost ~$10K+ for attorney fees; documentation and USCIS application fees). I know because I had to go through that asinine process years ago when my ex-employer (big corporation) sponsored my green card.