He also makes the point that the likeness of Captain Seljanus on the cover doesn't really mesh well with the description given in the book.
Indeed not. The in-joke behind the book was that Sejanus was the namesake and descendant of the historical Lucius Aelius Sejanus, a character who was played in the miniseries I, Claudius
by Patrick Stewart (in a curly-haired toupee). So presumably Dvorkin wanted Sejanus and Picard to look much more alike.