I would disagree 100% with this statement. Essentially every carbohydrate you ingest is broken down into sugars, whether it be cookies or whole wheat bread. Also, there are different types of sugar. The majority of sugar found in fruit is fructose, which is broken down in the liver and can be used to replenish liver glycogen. The liver can hold around 90-110g of glycogen. Other refined sugars are sucrose, which breaks down differently in the body and are used to replenish muscle glycogen. Energy requirements per person will vary greatly based on a variety of factors, but the 30g statement simply isn't true.
Its possible that this statement could be true for a completely sedentary individual. But if you're exercising daily, you're using far more energy (glycogen) than 30g per day. I think its false to assume that all carbohydrates and sugars are created equal, but you body can definitely utilize more than 30g of sugar per day if you are physically active - especially post workout. If what your coach said was true, I'd be reallllll fat, lol.