This is a bit of a guess, but might the 'one type' refer to the agent selling products from only one insurance company? (Agents either sell insurance from one provider only, in which case they're 'captive', or from a variety, in which case they're 'independent'.)
The other alternative that I can think of is that 'general' insurers are selling all kinds of insurance - life, accident, home, car, etc - whereas 'single type' agents sell only one kind - e.g. just life insurance or just non-life - and 特別 might be specialized, eg just selling car insurance.