I want to know the answer to the following question:
How do some camera designs give some EI choices?
All the background I'm provided with is that "For digital photo cameras ("digital still cameras"), an exposure index (EI) rating—commonly called ISO setting—is specified by the manufacturer such that the sRGB image files produced by the camera will have a lightness similar to what would be obtained with film of the same EI rating at the same exposure.". Is that enough to answer the question?
Answer: no