IMHO: It depends on the use and the equipment installed for that use. You could have a 10,000 sq foot building that has an assembly line that takes 75 people to operate or one that is fully automated and only needs 10 people to operate. I will always require the egress be designed to handle what the Table has listed However I am open to discussion about the number of plumbing fixtures that may be needed to adequately serve the workers.
FYI: Manufacturing in the 1988 UBC was a 200 OL factor and a B-4 occupancy. There wasn't an F or S categories in the code during that time frame
1004.5 Areas without fixed seating.
.................. Where an intended function is not listed in Table 1004.5, the building official shall establish a function based on a listed function that most nearly resembles the intended function.
Exception: Where approved by the building official, the actual number of occupants for whom each occupied space, floor or building is designed, although less than those determined by calculation, shall be permitted to be used in the determination of the design occupant load.