Permission : Allow "All File Access " message is maybe too scary

The default message about the "All File Access" permissions is too scary.

Most of our users don't seem to care but some of them don't understand why they should do that and don't grant this permission.

But importantly, they don't understand that they can grant "Allow access to media only" and continue to use VLC with standard Google medias.

Maybe we should at least have a link to a webpage somewhere to explain the situation in details.