As we read the standard, we find the following definition:
Signature, Enveloped The signature is over the XML content that contains the signature as an element. The content provides the root XML document element. Obviously, enveloped signatures must take care not to include their own value in the calculation of the SignatureValue.
It basically says that the enveloped signature must be a child of the element being signed.
If you sign some deeply buried node with embedded signature, the signature block will go into that node.