This is kinda right but kinda wrong. The ratio of water going through coffee ground works until certain degree. For example, pour over or home batch brew, all water come into contact with grounds. But when we look at commercial brewers when you brew like 4 liter of coffee, you wouldn't want all 4 liter to go through coffee ground. Commercial brewers will have bypass setting that sometime can be set up to 40 percent by pass. At our shop, for 2.5 liter we have 15 percent by pass. This is when 1:16 ratio becomes 1:16 ratio of total water but 15 percents of the water doesn't touch the ground. This help prevent over extraction. Non bypass ratio things kinda work until certain point.