Not so, I'm afraid, since neither the height or the width of the space available to a passenger has changed. With two dimensions held constant, any change in volume is directly proportional to the change in the third dimension (seat pitch).

However, the change in knee room is proportionately much larger than the change in pitch since the space occupied by the seat itself doesn't change. To take an extreme example, a seat pitch of 26" might leave one inch of space between the front of the seat cushion and the back of the seat in front. (It might be some other number; I'm not on an airplane right now so I don't have anything to measure; doesn't matter.) If pitch is increased by just one inch to 27", knee room would double. Actual E- knee room is probably around 10". Adding 4" to the seat pitch, which is only about a 13% change in pitch, is a 40% improvement in what counts. That 40%, or whatever the number is, can feel really big.