The above chart demonstrates that small changes in intramuscular fat can have a great impact on the price of beef subprimals. As trim levels decrease over the years, the line for acceptability will likely shift to the left. That muscle is always present in constant ratio and proportion to bone. With increased length of loin and rib sections, the flank and plate sections are longer, too. Thus, no net effect from a percentage standpoint.
Muscles grow in concert.
Thus, as you select for increased muscle in the round, muscles in the chuck will also increase. The reason why different prices are paid for different products.