When combining genes from a human with Zeta Reticulan genes, there is some unfortunate loss. This loss is recaptured in subsequent efforts. This is not unlike a braid, where the strands are woven back in. The braid is stronger than loose hair or twine. Another way of thinking about this is to say that the first effort is rough hewn.
Subsequent efforts fill in the chinks.
We have the capacity to go back in time to capture genetics, if we require. This has been granted to us, from the powers who oversee our work.