2. what does it mean if a paint sample "matches" a known sample from a vehicle? does this indicate the same source? why or why not?

The meaning of a paint sample "matching" a known sample from a vehicle means that the paint color is the same as the color that is already on the vehicle, or it is the same paint color that the company of the vehicle used on their cars.

This probably indicates that it is from the same source because a car company usually doesn't use a color that you can buy in the store. You usually have to order it directly from the company itself so with all that being said it is probably from the same source.