[itp]

No, it's deeper than that. They are describing the capabilities of a process handed a file descriptor, which means it does not have a path at all. There's no way to resolve '..' relative to no path.

Compare that to a POSIX system where a directory has an actual child which is a reference to the directory's parent whose name is always '..'.

The talk about resolving '..' is merely a demonstration that the behavior of "cd .." can be supported/emulated in a context where you have both an open directory and corresponding path, without requiring that '..' literally exist.

[loeg]

To add to that, as the document writes in the very first section, it can sort of be thought of as a chroot. You can't .. out of a chroot; there is no "..". (Yeah, it's not exactly a chroot; that's well covered in the document.)