The 350z and 370z have similar names and similar features such as vdc and traction control but the cars are very different with a different engine, platform, automatic transmission, and vdc.
I don't think the 7 speed is the same 5 speed transmission with two more gears and a new torque converter just because they both have down shift rev match and asc. Also, the 7 speed doesn't require fluid change and weighs a bit more than the 5 speed. I think transmissions get completely redesigned to have better performance, durability, and efficiency, just as cars do.
The 5 speed was very slow to shift and the shift time wasn't consistent. I'm guessing this was because the 5 speed wasn't designed from the beginning to shift quickly.
The pictures shows two different transmissions.
