The 3D lines exported to DGN contains length and width as Items. Problem is the DGN is missing the Item types library "Annotations" which the lines uses. It means that no report works with this DGN as the Items are not listed. The export is wrongly implemented.
If not mistaking, this is already part of an ongoing support ticket (CS0283635)
Support team is in touch to understand what is wrong in current implementation and following 'up on this, a fix could be appended if required.
Best regards
Please contact me for more information.
Without Item types these Items become orphaned and unable to use it with report tools.
It similar like creating text without defined text style, which is outdated and not recommended approach.