I don’t know that insistence is the right way to phrase it. Sir Patrick and Brent Spiner are good friends, IIRC Nemesis was written by Spiner’s old flatmate and best friend. As such the wants of the actors started creeping into the scripts, not out of insistence per se, but perhaps more out a natural affect of a close working relationship. Sometimes a healthy distance is most important between a writer’s room, and the cast.