The pattern and filed area dialogs work similar and "do" something similar. Why do you end up with two differnt element types. Why is it not interchangeable. This is more than ripe (dated)
In dwg you end up with a mess when you with patterns and fills.
And the functionality to edit patterns is also often leading to confusion for users.
Pattern could be a fill atribute same as it can have gradient fill it could have texture fill and so on.
Why should a filled element be patterned? I'd say AutoCAD is backward there, and always has been. Fill is an attribute of the element itself. Pattern is something special. Makes sense to me. Having to "fill" an element with a pattern in the one that doesn't make sense to me