User blog comment:TheWarrior29/10 Strange things in the Visual Guide/@comment-1984959-20140414035318

Regarding the reliability of any of the Visual Guides, I'll be fair and say it is for one's opinion. An obvious fact is that if it's not shown on screen, it has potential to be non-canon. That being said, I cannot deny that, depending on the topic in question, Visual Guides are the best bet for answers. Reason being that, according to Wordplay's "Ends of the Earth" Tale from the Set, Terry did help edit the first Visual Guide (maybe both?), including adding small details as naming Anamaria's boat as the Jolly Mon - information that was never revealed onscreen.

On the subject of "strange things", I can only say it's because of the universe we geek out over, and Gore Verbinski's Pirates trilogy (which the first Visual Guides covered) tend to be strange in and of itself. A user from KeepToTheCode forums said it best, that Gore "was more ambitious and I think he has a better eye for the absurd."

If nothing else, as another possible theory, you could go with the explanation that the unconfirmed-onscreen information may have been rumors or legends. Certainly the examples of Jack Sparrow's many legends tend to be stretches of truths, especially the "water through his veins" bit. But that doesn't necessarily mean one has to rule out Visual Guide info.

And I hate to break it, but almost all the info is correct and/or relevant in the POTC world. Some may be different because of later spoilers(i.e. Tia Dalma being "charmed by the appearance of Will Turner"), but majority of them are answerable with already-established canonical info.