Steps to reproduce:
Create a space with 3 versions
Create an unversioned space
Copy a page from the unversioned space into the versioned space
The editor opens and shows that this page is created in version x
Save the page
Either the page is in version x or the editor says that it will be created as an unversioned page.
While the editor says "version x" the page is actually saved as an unversioned page
Furthermore, when editing the page for the first time after copying, it gets created in all versions, which makes it quite hard to copy a page into a single version in a space.