Big Bear used to be fat (hence 'Big'), old model may have been used for flashback. He lost weight because of his crack addiction: that's why CJ and Ryder were so upset when they saw him at B'Dup's house in the Grove.
Voice lines are because at same time as beat down on b'dup you have to take over territories, R* were probably planning to have him help you but maybe coding got complicated. This is consistent with "All Terrain Takedown."
6:06 says take over all Vagos territories which is a lot to expect from average player, the mission was probably cut for this reason.
