Hello Paul,
Tina Jin and I tested this, it looks like we are able to reproduce the issue using this webmap (7fa70e3e030143e4a112ba4e3ce003c2) with offline map areas.
Both the symbology and the layer name of the MMPK are coming from the feature layer instead of what being set in the webmap.
The webmap in ArcGIS Online Map Viewer,
Webmap in AppStudio Map Viewer with the same Layer name and symbology.
Offline Map Area in AppStudio Map Viewer (see the points has plain black symbology and the layer name is not the same as in the webmap)
Can you please submit this issue as a BUG thru
Esri Technical Support ? So that we can track and prioritize this accordingly.
Thank you,
Erwin