Anyone knows memo regarding leaving US w/o receipt?

My lawyer told me that H holder does not need to wait until he/she gets 485 receipt letter. She said it used to be a law that people file AOS have to wait until he/she gets receipt, then leave US. Since last August, a memo comes out, it states that H holder could leave US before getting 485 receipt letter. Anyone knows this memo? Can you tell me the link? Thanks!