It seems to me that white does better with this exchange:
Even if white tenuki's at 6, black dominates the bottom and center while white gets essentially no compensation. Note that black can follow up with something around k5 to take the entire bottom, or later play around l4. On the other hand, white's thickness is almost completely surrounded by strong black positions and ends up practically useless. The variation in the game gives white an attack on the black stones at top, strengthens white's center position and gives black less along the bottom (m5 stones).