Good summary and insight into the Hu Jintao leaving incidence.
This is best explanation by far or what went down. For those who do not speak Chinese, there are several points made here.
1. The vote Hu made was done in the morning, so he would have already seen the list. This happened at around noon.
2. It is likely Hu was confused and think that he needs to vote, which explained the confusion and all the help the guy sitting next to him was trying to give.
3. The young man who manhandled him was his own body guard for ten years, since he fully retired. Even though he bore some resemblance to an aide from Xi, the aide was 1.9 m tall and this guy was only 1.8 m. They all deferred to him to help Hu. Maybe he felt close enough to Hu to help him this way.