Not true. Command grab is for extra damage and a pure 100% initial proration. Pretty sure 2D is something around 80/80, whereas with this setup you get a little extra starting damage and a [100]/80 for the 2D. So the grab is vital, and also a reason this combo is viable.
EDIT: 2D Prorates 80/87, so using the command grab to set it up you get 100/100 initial, 100 on the second grab hit, 87 on 2D, 91 on all j4C's and etc.
Alternatively, if you started on 2D, you get 80 then 87, then 91 on all j4C's. So if you take both proration percents at, for example, the second j4C, you have.. I think something like ~75 for the first one, and ~56 for the second one. A huge difference, but 2D would still probably net you 4kish.. it's just, the command grab or j4C starter are gonna get you the 7k gold.