Read Thread: Old logbooks
What was once considered the State Of The Art lgbk for this hobby had its definite advantages. One of which was being able to separate the thicker index card pages of even the most waterlogged lgbk. However, over half of its pages may be illegible due to the excessive bleeding of dye-based imprints. Whereas, all the pigment imprints will look even sharper and more vibrant on the wet pages.
Thanks to the worthwhile efforts of Rocklun (and others) letterboxes and its contents, having seen better days, can often be restored and replaced in a new watertight container for others to enjoy the trek to find. Thankfully, there are a few like Rocklun that enjoy the challenge of restoring a worthy letterbox and its contents that others may view as an inconvenience not worth the effort.
I'm not convinced this is a dye vs. pigment thing. There are dye inks that are waterproof, and there are dye inks that are "washable". And the pigment ink that I use, Brilliance, has not proven to be all that waterproof; it tends to blur when wet.