This video of a sofa upholstery cleaning shows what a difference a professional upholstery cleaning can make to a heavily soiled piece of furniture. This type of cleaning is called hot water extraction and its very effective at removing soil build up and heavy spotting. It can used on most upholstered furniture, even ones that only recommend "s" type, or solvent only cleanings.
Most of today's materials that are used in upholstery can stand up to a wet cleaning. That doesn't mean that precautions should not be taken. All upholstery showed be tested for colorfastness and browning before any type of cleaning is performed. As a professional upholstery cleaner in Tampa FL I always test my fabrics and materials before cleaning them. It pays to double check by testing multiple areas when dealing with cotton or other natural fibers.
The furniture in this video looks to be heavily soiled but the darker areas aren't just soiled they have been wetted with a pre-spray to help release soils and emulsify dirt before the hot water extraction is performed. Most upholstery coverings get darker or dingy when they get wet. The cushions in this video are not quite as dirty as they seem, but doesn't mean they didn't need a good cleaning. There is still a good amount of soil on these off white cushions. They look to be upholstery with a heavier material which adds to the cleaning difficulty. All in all they look to be doing a good job cleaning this off white sofa.