Import "Keep Folder Organization" produces folder and a sub-folder with the same name?

To give context for others, this is when importing folders into Photos. There's a checkbox labelled Keep Folders (previously Keep Folder Organisation) that tells Photos to create an album named after each folder on disk. It's useful if you've already organised your pictures outside of Photos and want to retain that.

I can confirm that for each folder on disk, Photos creates a folder – under My Albums – and then places an identically-named album within that. Note the distinction between folders and albums in Photos terminology.

This seems unnecessary until you consider the possibility of subfolders — that is, folders within folders. Because there's no such thing as a "sub-album", importing a hierarchy of folders (on disk) requires the creation of a folder (in Photos) at each level. But a folder in Photos can't directly contain pictures, so it needs an album inside!

It's reasonable to suggest that Photos needn't create a folder at the deepest level of each branch, i.e. when there are no subfolders. But it would need to be programmed to make this distinction. You could always send feedback to Apple.