Industrial standard for interference fits is to lightly grease or oil. Or do nothing, which means lightly oiled, since all parts come that way.
Shimano BB’s out of the box have a small dab of grease on each taper surface, and a thin coat of oil all over for corrosion protection.
A lot of people do not grease, and it works fine. Keep in mind, to be truly grease or oil free, you would have to clean both surfaces with a solvent.
Square tapers get rounded & mangled for a lot of other reasons.
However
steel spindle + alloy arm = no grease
steel spindle + steel arm = grease
titanium spindle + any arm = anti-seize
The above seems to be another ‘skool’ of thought