A public application may constitute a "public" document.
When the specification is not published in printed form, but published in an official magazine, and anyone can check or obtain a copy, the public can fully obtain the specification, thus forming a "publication" in the sense of 35 U.S.C. 102(a) and (b). See Wyer, 655 F.2d 22 1, 210upq790 (ccpa1981).
That is to say, the "open" patent application has not been published publicly, but its existence has been publicly disclosed, so the public can take this opportunity to request access to the application-so it is open.