Well, the surface of the molded grip is round, and the back of a 1911-style grip panel is flat.Is is possible to just glue on a grip with out grinding out the plastic? The only thing wrong I see would be that it would be a little fatter.
I suppose you could could take a dremel and round out the back of a grip panel to fit the contour of the molded grip... but then you'd have to do that every time you changed grips.
If you grind the frame, you only have to do it once.
That's my take on it anyway.