GIPS : After-tax Return Calculation Methodology

CFAI text V6 P332 & Q27 This topic is not in the scope of LOS. Do you think we shall study ? Though I know that CFAI does not say that those materials out of the scope of LOS will not be tested, but my brain is overflowing due to my memory capacity is not enough and the memory capacity can not be increased. Just like to know your opinions.