In #21024 rich-image was implemented with block filters as its own "block" which modifies both the image block and the cover block.

Moving the feature as a block-editor component would allow the toolbar section to go wherever in each block it is applied to and it would allow other block developers to take advantage of the rich image editing in their own blocks.

Doing it the old way had the benefit of being entirely decoupled from the block it is modifying. It was essentially an overlay to the existing block. Unfortunately, this also meant that the editing tools could only be prepended or appended to the existing toolbar. It wasn't possible to put the rich image controls in-between the alignment and replace buttons. Furthermore, it limited the features to only the blocks which it specified.