Before revision:  Here we discuss how some of the most popular implementations of this machinery assume a strong condition on the ergodicity of the cell cycle duration ensemble and that two common definitions for the term , ergodicity, while identical in an ensemble with a fixed number of individuals , are in fact unique constraints when the ensemble is growing.
After revision:  Here we discuss how some of the most popular implementations of this machinery assume a strong condition on the ergodicity of the cell cycle duration ensemble and that two common definitions for the term ergodicity, "a single individual observed over many generations recapitulates the behavior of the entire ensemble" is implied by the other, "the probability of observing any state is conserved across time and over all individuals" in an ensemble with a fixed number of individuals , are in fact unique constraints when the ensemble is growing.