Request so that credit card processing through Authorize.net is independent of web host permissions of the encryption directory (so it can be used on any shared hosts).

Understood, it's to do with the permissions and whether the hosting company is willing to grant them if one is on a shared server. Just making a suggestion, as PowerDnn and 3Essentials are popular and well rated hosting companies for DNN websites.  Compatibility could be a big thing for people.