This was a stupid change that added absolutely nothing of value, introduced unnecessary UI complexity and the only reason the GIMP developers did not revert despite all the users requesting it is arrogance as they believe to know better than their own users (which is to be expected by anything related GNOME - see the file dialog woes).
Of course GIMP is free and open source so it isn't like they owe anyone a better UX or anything, they could replace all brushes with bananas and drop all file formats except BMP and nobody would have any right to demand anything from them. But at the same time that doesn't (and shouldn't) stop others from calling stinky something that smells bad.