Question

Why is it that females tend to have lower accuracy for their EPD's?

Answer 1

EPD refers to Expected progeny differences. EPDs provide estimates of the genetic value of an animal as a parent.
The differences in EPDs between two individuals of the same breed predict differences in performance between their future offspring when each is mated to animals of the same average genetic merit.
EPDs are calculated for birth, growth, maternal, and carcass traits and are reported in the same units of measurement as the trait. Virtually all performance data that relate to the animal of interest are used to calculate its EPD. The genetic merit of mates is accounted in evaluating progeny information.
EPD values may be directly compared only between animals of the same breed. EPDs are most useful to directly compare individuals for a trait of interest.

Accuracy can be defined as the relationship between the estimated EPD of the animal and the "true" EPD of the animal. This relationship is expressed as a number between zero and one.

Accuracy is primarily a function of the amount of information available to calculate an EPD for any given trait. Information, primarily in the form of performance records, is derived from several sources to estimate EPDs on a given animal.
Since, females have similar sex chromosomes, they produce almost same type of gametes.
Accuracy is dependent on several different factors including trait heritability, number of phenotypic records on the individual and its relatives, and number of records on any traits that are genetically correlated. Because the heritability cannot be influenced directly, recording the phenotypic performance of the individual in question and its progeny is the easiest way to build accuracy for an EPD on a particular trait.

All of the above are lesser in females. So, EPD accuracy is low in females