Kevin
The bars in the review screen only show base design for all teams, for this reason you can calculate how many dp you will receive from research.
I didn't explain very well, I'll try again...
The number of research dp you receive is calculated on the difference between your BASE design and the strongest BASE design in the attribute you are researching. If total design (including supplier bonus) were to be displayed on the review bar chart you would not be able to calculate your best research strategy because you don't know what suppliers your competitors are using.
Does that explain it better?
I see no reason to worry about car performance being linked to the review line graph, it is just to help you with your research strategy.