for the most part, these children would be adults by the time such a thing occurred.
Of course, that part is true. It's damaging enough for those of us who are rejected by our flesh-and-blood family because of WTS dogma, whether we are children or adults. I mean, I'm looking at my 40s in the rear-view mirror, if you know what I mean, and to know that my JW parents would sooner associate with creepy JW people with inappropriate tendencies toward teenaged kids, and non-JW relatives who drink to excess, fornicate, commit adultery, smoke, etc. rather than me - for the simple reason that I cannot, after careful consideration, believe the way they do - is extremely painful.
When you take the case of an adopted child, whose biological parents couldn't keep them or didn't want to keep them, being made to feel special by their adoptive parents "We chose YOU!!" knowing that their bio parents chose otherwise, I would think the feelings of rejection would be magnified exponentially if they were to be shunned by the adoptive family as well. I can only imagine the mental gymnastics involved when an adopted child, who is raised in the JW religion, figures out that it's not The Truth™, and knows the ramifications if they ever want to leave the JWs. They truly may not have a single blood relative that they know of to turn to - their feelings of isolation / captivity must be extremely poignant.