Yeah, the checkmark can be made to reflect only the hash -- but it wasn't intended to be a 100% exact match. It's designed to let you know you probably have this file -- hashes are a surefire way, but the filename is also a pretty good way. Perhaps the filename should also include a size check, ensuring that the two are similar sizes? Or maybe a blue instead of green checkmark for the filename matches. Grouping is still done only by hash.