Maybe they updated their terms in recent times which allows them to hold the user's funds forever.
Not anywhere in the US ToS that I can find.
Just now I went through their updated terms still the withdrawal of funds from the terminated account is still in place.
You will be permitted to transfer Supported Digital Assets or funds associated with your hosted Digital Asset Wallet(s) and/or your USD Wallet(s) for ninety (90) days after Account deactivation or cancellation
So the support is liable to give a reason why the funds are on hold, but we know how sloppy their support system is, even it may take months to resolve simple issues in coinbase platform.