xorlo is an official part of the Lojban Language. The Complete Lojban Language does not contain information about xorlo, and is no longer guaranteed to be entirely accurate. The Committee for Developing Lojban (BPFK) voted 11-0 to include xorlo in the official record as a part of the Lojban language. The proposal is not finalized until the BPFK declares their work finished, but it is extremely unlikely to change, as it has become an integral part of how the language works conversationally.
In essence, xorlo changes the meaning of two particle articles in lojban: lo, and le.
lo as an article used to indicate that you were talking about a set of objects which are truthfully what you claim they are. Nothing about them indicates that they would be anything else. For example, "lo jgena" meant "some things that are, to our best perceptions, knots."
Now, it doesn't say anything about perceptions, or the truthiness of what it is. It just means "any or some." It becomes the most generic article you can use in lojban, in place of anything else, because it is vague. "lo jgena" now means "any/some knot(s)," without qualification or ulterior statement about veracity.
le as an article used to mean "some things I have in mind, which I am describing." For example, "le jgena" meant that you had some knots in your head. The change to le is very minor in this context, and its pure meaning hasn't actually changed. The only difference is that it now exists only to be used when you have specific images of something in mind. Now, if I tell you "le jgena," you know I mean something more specific.