Transferring assets to avoid creditors or potential creditors is against the law
The first part is correct, but the second is not. It's perfectly legal to transfer assets if that transfer happens to have the effect of making the assets unavailable to unknown future creditors. Under fraudulent transfer law there has to be an intent to avoid a specific liability. By making transfers when the organization is in good financial condition, they stay out of constructive fraudulent transfer territory also. And even if transfers are determined to be fraudulent, there is a limited look back period, so after enough time passes even a fraudulent transfer can't be reached. Under bankruptcy law, preferential transfers can be recovered from a bankrupt even without meeting the above, but at most you can only go back one year. I'm not an expert on trusts, but I'm sure if they wanted to, they could move assets into some kind of asset-protection trusts outside of the U.S., or transfer assets to another Watchtower related corporation overseas and after a while, those assets couldn't be reached to satisfy U.S. judgments. (Or make it so expensive to reach that judgment creditors will settle for pennies on the dollar). As an example, it's not uncommon at all for doctors to make some of their assets hard to reach just in case there is a huge malpractice suit. You just can't do it after you commit the malpractice.
That said, I highly doubt asset protection is a significant factor. If the WTS were to face massive liability, the new branch land and buildings would still be available, as would all of the assembly halls and at least all domestic assets. I'm sure they aren't planning on that happening.