The present study examined the posited structure of the Wechsler Intelligence Scale for Children--Fifth Edition (WISC-V) ancillary index scores with normative sample participants aged 6-16 years (N = 2200) using a series of confirmatory factor analyzes (CFA) with maximum likelihood estimation. CFA results supported the retention of auditory working memory (AWM) but not quantitative reasoning (QR) as narrow dimensions in an extended WISC-V measurement model. Additional results from models explicating the structures for each of the posited ancillary composite-level indexes (nonverbal [NVI], general ability [GAI], cognitive processing [CPI]) provided support, in part, that these indexes represent global dimensions with differing degrees of generality. Though some of these scores may be used in the manner intended by the test publisher (e.g., comparing and contrasting performance on different composites, specific learning disability identification), provisional limitations for using the ancillary indexes as a focal point of clinical decision-making are discussed.