nope. x.org is a subdomain of org.
From RFC 1034:
"A domain is identified by a domain name, and consists of that part of
the domain name space that is at or below the domain name which
specifies the domain. A domain is a subdomain of another domain if it
is contained within that domain. This relationship can be tested by
seeing if the subdomain's name ends with the containing domain's name.
For example, A.B.C.D is a subdomain of B.C.D, C.D, D, and " "."
so as an example,
X.Org Foundation is a subdomain of x.org, which is a subdomain of org (which is a subdomain of " ").
See section 3.4 for an example which states that .mil, .edu and .arpa (as examples) are subdomains.