The document is known by Watchtower appointees and is asked for by those appointees for sake of JW parents having the opportunity to sign it.
I did not know this ever, even though you conclude that I should.
Fisherman, you already said on page 2:
So, the parents are not agreeing that the hospital give blood to their child by signing the document and neither is the WTS by choosing to allow the use of such a document.
HLC are appointed by the Watchtower and must follow Watchtower instructions. Various HLC's are aware of this type of letter, as the newspaper article shows.
A template for a 'letter of understanding' may be held on file by HLC, or requested. I don't know.. The important point is that the Watchtower allows it to be used, as you admitted.