Franc, I like your reasoning.
If anyone doesn't think that grease or oil is an attractor to dirt, put some grease, oil and then nothing on paint stirer and let it stand outside and see what was "attracted" it it.
As far as comparing an auto's intake and either a babbited bearing or roller bearing, they ride on a thin film of oil. In the 50's, early 60's autos intake cleaner had oil in them to stop the particles from going into the carburetor. High performance ones like K&N still do this, but we are talking hinge pins and not rpms.
I don't believe in using grease, but use a lite coat of oil when cleaning the gun after use. If I did use something else it might be Molycote or a graphite powder, which to me is a better lubricant than oil or grease and will not gather dirt or foreign matter.
