You kind of get the idea by saying that it's a lazy way to color grade correct. However, trying to recreate what film convert is on your own would require a lot of experience color grading to the point where you would have to create your own LUT. One of the benefits of film convert is not only that it recreates different film stocks on your footage, but also that it adjusts that "film stock" so that it adjusts for whatever camera you shot on. For example, the same film stock LUT will look the same on both Sony and Canon cameras, meaning that no matter what camera you use it will accurately recreate that film stock. This also helps quite a lot when trying to match shots from two different cameras, since you can just tell it to adjust for each camera individually on a shot-by-shot basis. Make sense?