What specfically is a "database feature class", as distinct from "feature class"?
For example in Catalog here we see 3 layers in an enterprise sql server geodatabase. The bottom and top ones are regular polyon feature classes created the regular way. The middle one is also a polygon layer, but is created with the Create Database View geoprocessing tool.

All 3 of them can be added to a Map in Pro and they behave identically in the map as far as we can tell for symbology, labelling, selection, etc.
Why does Catalog not see the view as Polygon type?
In another ent-gdb I have access that is oracle hosted instead of sql server there are spatial view layers, but they area seen the same as normal FC. I don't know how these oracle spatial views were created.

How do we get our sql server database views to be recognised as layers with geometry types before adding them to a map?