In Arc Map, one can fill multiple holes in Polygons: 

Filling all holes in selected polygons—Help | ArcGIS Desktop 

This does not appear to be the case in Pro (perhaps I have not yet found the tool yet?) 

Fill a hole in a polygon feature—ArcGIS Pro | ArcGIS Desktop 

On the same topic, in the Arc Map production mapping tool bar, making a polygon whole is a single button operation. Fill a hole in a polygon feature—ArcGIS Pro | ArcGIS Desktop appears to consume very many steps. 

Continuing, again, with the production mapping toolbar, poking holes in a polygon is once again a single-button operation. Haven't found the same very-few-steps workflow in Pro.