As with cushion cuts, many princess cut diamonds will be cut for heavier weight. This extra weight can come at the expense of beauty.
Many grading laboratories, including GIA, do not assess the optical performance of fancy shaped diamonds.
Without enforceable guidelines, manufacturers tend to plan for the highest yield possible, resulting in princess cut diamonds of great depth, concealing weight in the body. The increase in ticket price incentivizes the weight prioritization.
As noted above, Some of the labs have begun noting optical performance in fancy diamond shapes. AGS and GCAL are among the labs that are marking this distinction.