First of all wd-40 is NOT water based, infact it contains no water at all.
Straight off the wd-40 website
"What does WD-40 contain?
While the ingredients in WD-40 are secret, we can tell you what WD-40 does NOT contain. WD-40 does not contain silicone, kerosene, water, wax, graphite, chlorofluorocarbons (CFCs), or any known cancer-causing agents."
Second, Surfacants lower the surface tension of 2 mediums when its applied, releasing the hold of the dirt from the metal. The surfactants break up the dirt particals and keep them suspended in solvant.
Once your done releasing the dirt from the metal, you rinse the wd-40/surfactants/dirt with water. Water also contains surfactants which release the hold of the solvent to the metal, thus getting rid of the solvent, that broke down, released, and is suspending the dirt from the surface of the bearing.
Then you dry the bearings using the hair dryer which evaporates the water from the bearing. The bearing now contains no more surfactants, so oil WILL stick like its supposed to, keeping your bearings spinning fast and lasting long.
As you can now see, wd-40 does NOT harm your bearings if used to clean/degrease with as long as you wash the wd-40 out when your done removing the dirt then dry your bearings quickly to avoid rust. However, if used as a lubricant, wd-40 will keep the dirt traped in your bearings and also atract more dirt, which will ruin them.