Revealing mistake: Near the end of the film, when Picard bends the pole down to stab Shinzon, the pole supposedly goes through him and out the other side, but the prop travels several inches down his waist. A shot later, you can see the prop pushing against Shinzon's clothing, obviously not piercing anything. (01:39:17)
Revealing mistake: In the scene just after Picard, Worf and Data arrive back on the ship with the android parts, while examining B4 Geordi is using a static prop tricorder (The tricorder is soundless and lightless) and when he closes it you hear the plastic prop closing, not the typical clicking tricorder sound.
Answer: Shinzon was always intended to be much younger than Picard - the whole point is that he's a Romulan project that was ultimately abandoned - he hasn't gone through the accelerated aging process. Patrick Stewart could not have convincingly played a version of his character who was that young. And Tom Hardy does bear a distinct resemblance to a young Patrick Stewart if you look properly.
Tailkinker ★