"13 There is no way to undo a dedication vow, taking back what we promised God. If a person tires of serving Jehovah or of living a Christian way of life, he cannot claim that he was never really dedicated and that his baptism was invalid."
There are two different things mentioned here: "Tires of serving Jehovah" or "Tires of living a Christian way of life."
Leaving the Organization doesn't necessarily mean one wouldn't continue living a "Christian" way of life. If a person dedicates his or her life based upon what they learn from studying JW literature and later those teachings are changed because they were wrong, then one could say that their dedication wasn't based upon accurate knowledge..
Even the 2 questions they asked me on the day I was baptized have since been changed. To me, the fact that these questions needed to be changed, indicates that what I originally agreed to or acknowledged at my baptism, was incorrect for some reason.
Besides all of the above, each Kingdom Hall is dedicated to Jehovah when it first opened for use and as we all know many of those "dedicated" Halls have been sold off. Apparently it is possible to un-do a dedication to Jehovah so long as there's profit involved.