To utilize Esri related readers and writers in 64-bit FME when you have ArcGIS Desktop installed (which is a native 32-bit application), Background Geoprocessing is required. Background Geoprocessing is available from your ArcGIS Desktop installation package.

ArcGIS Pro is a 64-bit application, therefore Background Geoprocessing is not required for Esri features to be accessed by 64-bit FME.

For further details on this issue please review :

1) https://knowledge.safe.com/articles/315/geodatabase-formats-missing-greyed-out-or-have-unm.html

2) https://knowledge.safe.com/articles/1517/notes-on-fme-and-esri-versions-and-compatibility.html