Yeah he said this in 2001, it might be a different meaning he had, but other heavy metal bands had their own meaning.

Besides, the way Dion did it is actually offensive in Italy, for example https://content.time.com/time/specials/packages/article/0,28804,1874098_1874099_1874139,00.html

The sign he is taking about supposed to be with fingers tilting downward or in level position, not point at specific person and without movement.

Also while he popularized it, he wasn’t first one it looks like it was first used by a rock band that was into occult in 1967.

https://vinylstories.ca/wp-content/uploads/image-asset.jpeg

Lol, also in the debut album of Coven, the featured song was called Black Sabbath, the name of the band Dio was in when he used the sign for the first time.

Ozzy was known for using a peace sign, Dio wanted something similar, but didn’t want to copy it, so he used the devil sign from Coven and then in 2001 came to with the grandma’s story to not make it look like he ripped it off.