No , the way it was working is that there were a "version number" for each file.
Some files remained Version 0, but some database file were updated in each DLC.
Each new DLC was "upgrading" some databases, like the camera.bin file .
The camera.bin file contains the position for the camera from the relative coordinates of the car for
each camera mode (bumper, inside cam etc...)
so, if you had DLC1 and DLC4 ; the game was using the camera.bin from DLC4 , which
was containing datas from DLC1, DLC2 , DLC3 too.
Each DLC was also containing a .XML file with actions to do when the DLC was initialize; ie. put this
car in this shop slots, send a message anouncing the new car etc.
Hope it helps !