The WTS almost always reacts to 1.)money 2.) politics 3.) money 4.) law 5.) money.
I find it odd that the letter is specifically asking for names. I can see the weird and wacky notions that are connected to data collection - the WTS has always been obssessed with numbers. But, to ask for the names is rather creepy.
Could the WTs be trying to distance themselves from people that they don't want to be held accountable for? As in..."Oh, we don't have to pay compensation out for their actions...they aren't even a Jehovah's Witness. See? We have proof. That guy? He ain't one of us!"