"I'm not sure how the letter you guys are talking about would not be construed as a formal disassociation in and of itself."
This is the danger, but the "Letter" prevents them from taking the Action of Announcing you as "No longer one of Jehovah's Witnesses", hopefully, as long as you threaten Legal Action if they do so.
Their Committee formed to decide if you have Disassociated yourself, the Elders Book says, is NOT "Ecclesiastical" , so how can they take any action against a proven non member, by a Committee with no Ecclesiastical Authority ?
They have missed the boat, yes, you did in fact disassociate yourself at the Date of the letter, but the time is gone, they cannot Defame the name of a person who is now a mere member of the Public and hope to get away with it.
The same would apply, if you have the letter, to an Ecclesiastical Judicial Committee, but if you committed a "Sin" as defined by them BEFORE the Date of the Letter, while still a member, you may be in trouble, but it may still help, so again Good Luck everybody !
It occurs to me also that the Org itself is unlikely to support the Elders involved, or even the Congregation, in a financial way, they will give advice, over the 'phone, once your Letter is revealed to them, to leave well alone, if they have a modicum of sense. If the Elders then go ahead, they are on their own.