When playing with this mod, my assemblers had a weird second input for sulfuric acid and lubricant showinbg in alt mode (not actually acepting liquid), and using that you could put lubricant into the data "pipe" of this mod, I checked in sandbox so i am not sure if it's posible in normal play, but I searched for the origin of the wierd second input for liquids and that was my conclusion.

I'm not totally sure I understand, if it's still happening, could you give me a screenshot? If someone comes here and has the same problem...

Just checked and this still happens on 1.1.4

It seems some recipes have a fluid box added to the assembly machine despite not using "data" in the recipe.
https://imgur.com/a/bi8KUjF

I haven't played in 5 months and just did a quick skim over my factory so I don't have a list of every affected recipe, the liquid concrete recipe from Crushing Industry was the first one I was able to find. There may be more or it may be a bug with how liquid concrete fluid boxes are set up.

I was unable to get non-data fluids into the data pipe as OP described.

Ok this is super strange, I'll try with the specific recipe from crushing industry, this is some funky behavior. Maybe that's something to do with some specific mods?