While I generally agree that online "Can" be more up to date. When I go to many of the Baja web sites I find the dates of the Updates and posts are years old and the site has clearly not been updated in a long time.
As for Moon handbooks. They operate just like any other popular guidebook the research is being done now (2015) for the 2016 edition. With computers running the process from writing to layout to the printing presses, time to publication has been shortened considerably over the old days.
All in all I have gotten as much (or more) bad information from the web on any given subject as I have from more traditional publications. It's not a panacea. Just another tool.