I know the Einscan-s promises around 0.1mm accuracy, but I don't know about overall shape accuracy,
the scans are build up out of several scans, and during the scans I can see some misalignment, but they are corrected with the scan is finalized,
if the software adjusts the shape to get the best fit, it could be that the final part is a bit "distorted" compared to the original.
I have not tested this yet, I am not using the scanner for engineering purposes

You should be able to correct the shape in cad afterwards, you would need to do that anyway, to repair all the small holes and attachment points for you car parts.
it will be difficult to get all the small seams or click attachments, the scanner just doesn't get into all the nooks and crannies.