It's the plot. There's no mention of Millet's blocked evolution in any of the Sayle series, so it's the plot, and Pax can get rid of his blocked evolution.
That is of course the plot needs, because millet's popularity is super good, has been buried foreshadowing, the author finally saw him fill the pit
It was on the Sayle, the Sayle War on Mars
Parks can undo his block Evolutionis. There seems to be no answer as to why he has this problem