Why does the list contain so many sub domains? Wouldn't it follow from facebook.com being meta owned that weird.subdomain.facebook.com is also meta owned?
And on your question: it is most often the case that a subdomain is owned by the same entity, but it is not a given. The most common thing is a CNAME to some site of a vendor. But you can go all the way to full subdomain delegation (this is the same as going from com. to facebook.com.).