a clone of Jean-Luc Picard. We also learn that he is dying because of this.
From the blood sample Shinzon provides, Dr. Crusher figures out why:
BEVERLY: The more I studied his DNA the more confusing it got. Finally I could only come to one conclusion... Shinzon was created with temporal RNA sequencing. He was designed so that at a certain point his aging process could be accelerated to reach your age more quickly, so he could replace you.
PICARD: But the Romulans abandoned the plan...
BEVERLY: As a result the temporal sequencing was never activated. Remember, he was supposed to replace you at nearly your current age. He was engineered to skip thirty years of life. But since the RNA sequencing was never activated, his cellular structure has started to break down. He's dying.
To repair the damage, Shinzon comes up with a convoluted plan to
capture Captain Picard and perform a full blood transfusion.
I understand that this requirement drives the plot, but was it ever explained in a novel or elsewhere why Shinzon did not simply activate the RNA sequencing to age himself?