Thanks for the correction. It's odd, because on memory-alpha under the entry for "Harrison" (not under the entry for "Ron Veto") they only list 13 episodes, which also matches IMDB.
My other two points are still valid:
1. There is no reason to believe Cumberbatch is playing the same guy named "Harrison", considering it is a common name -- although the movie will probably never specify one way or the other if it is the same character.
2. Considering that Harrison's name was only associated with an on-screen character once (in Space Seed), AND that identification of the character was ambiguous, we can't be 100% sure that Veto was "Harrison": There were two actors seen on the screen, and the two were identified as Thule and Harrison -- but we can't be sure which actor was Thule and which was Harrison. Therefore, Veto may have been "Thule".
Having said that, considering Kirk was naming the people in that scene in a certain order (counterclockwise around him), it does seem to follow that Veto was Harrison.