@gaetawoo is right. The documentation is weirdly worded around this, but directory archetypes require also the --kind parameter (which is the directory name in the archetypes directory).
I don’t think they require the --kind parameter. Only if your section destination is different that the archetype name. Which is typical. The key is that you cannot create a new index.md you must create a new folder as your content.
Also a hint to any snoopers, if you want to make sure some sub-folders of your page bundle archetype also are created, you need to have a file in them in the archetype. If they are empty, they won’t be created. Just a simple 0 byte .keep file in the folder.