Items that have the flag of 'hidden' are not shown in fnei if you dont want to see them (or shown with the red background). Fluids (that use the .hidden variable instead of flags) are all shown even though some of them are hidden.
Example: when running angel/bob the bob fluids that are set to hidden by angel mods (due to having their own versions of same) are still found in FNEI even though they dont have any recipes that use / produce them anymore, cluttering up the screen.
From what I have seen in the code, it seems like you check for the hidden flag on the items and dont show the hidden items unless the user enables showing hidden items, but fluids are just passed on without checking if they are hidden or not.
Not sure if this is a bug report or a request for a feature (to make hidden fluids also not be visible unless requested), but il just leave it as a bug
