Disclaimer I am no electrical engineer and have had limited experiences soldering components on circuit boards. But from all the tutorials I've been through, I agree. There are risks of damaging the NAND chip while desoldering and/or re-soldering chips on the board. Since there is the only piece of hardware with the information, perhaps the Feds aren't going to risk the chance of destroying the evidence all together after all they made the mistake of changing iCloud password already.