Network Common Data Form (NetCDF) files cannot be specified as input to a mosaic dataset when using the NetCDF raster type within the Add Rasters to Mosaic Dataset geoprocessing Tool.
This has been fixed in ArcGIS Pro v1.3. The Add Rasters tool in ArcGIS Pro 1.3 behaves much in the same way as ArcMap, allowing users to pick the type of input and then browse or drag and drop the input.