Why decrypt movie if dvdfab burns good backup

I’m wondering what physical difference it makes to decrypt a movie first, when dvd platinum makes perfect backup?

Your software is decrypting first as it makes the backup.
It is not possible to back up a commercial movie with out decrypting first regardless if the movie is being burned to a disk or saved to a hard drive.

I decrypt the movies to my hard drive first and then burn the move. This is not necessary but I prefer to save the movies to my hard drive so if there is a burning problem I can play and tinker with it to solve the problem.