I just downloaded the NP April 2018 upgrade files and release notes and it looks like they fixed it in this release. I haven't tested it however, just going off what I saw in the release notes, per below...
Friendly name was not given to the report while using dynamic name
Jira issue ID: OP-6821
Reports with Dynamic Naming option enabled, and the Friendly Name set, arrived via email as
attachments with the Report Name in lieu of the Friendly Name.
This bug only affected the September 2017 version.