It appears that Boilerplate Posts with featured images only work correctly the first time it’s published to a child site.
If the same boilerplate post is published to other child sites, the featured image is not applied. The image appears in the Media Library, but there is no database record on the child site for the featured image association.
Also, on the first child site, the Media asset is duplicated and the post is updated to use that duplicated asset filename.
I retested using 4.1-beta3 and the featured images are being attached correctly on child site posts.
However, the issue with images being duplicated in child site Media folders is still there. The images are duplicated each time the boilerplate post is republished.