Let's not forget IFC and the biggest misuse of standpipes. Many years ago schools were having to fight against a fire pump because of a stage. (An actual stage and not a platform that an Architect mislabeled.) The class II has always been hit or miss. For the longest time, everyone placed 2½" connection (Class III) with reducer to 1½". These are just about gone. The code is behind somewhat in catching up with this. Remember seeing 1½" hose stations in Big Box retails? Most insurance companies are having them or have had them removed. It is all about getting the public out and giving the trained professionals the tools they need.
As you can see below, the IFC still requires standpipes on stages, but you can drop the Class to a II if sprinkled.
905.3.4 Stages. Stages greater than 1,000 square feet (93 m2) in area shall be equipped with a Class III wet standpipe system with 11/2-inch and 21/2-inch (38 mm and 64 mm) hose connections on each side of the stage.
Exception: Where the building or area is equipped throughout with an automatic sprinkler system, a 11/2 inch (38 mm) hose connection shall be installed in accordance with NFPA 13 or in accordance with NFPA 14 for Class II or III standpipes.905.3.4.1 Hose and cabinet. The 11/2-inch (38 mm) hose connections shall be equipped with sufficient lengths of 11/2-inch (38 mm) hose to provide fire protection for the stage area. Hose connections shall be equipped with an approved adjustable fog nozzle and be mounted in a cabinet or on a rack.
Hope this helps.
R/
Matt