Since money is fungible, it is still adding to Iran’s coffers and frees up the government to spend on other things, such as supporting terrorist groups like Hamas.
"The $6 billion has not been accessed completely by Iran yet, but the fact of the matter is if you have a credit on your account for $6 billion, typically, people count that as access available today, tomorrow, whenever, so you start reworking your spending budget.
And by doing so, you put yourself in a position to use that money even though you have not had access to it yet. So the $6 billion that they know they’re getting, they’re using already." - Tim Scott