Your quote. They did what was minimally required. Which is all they are entitled to do. Leniency? They don’t have to worry about that. Vance has to prove his case. And explain why he is criminally prosecuting something that has never been criminally prosecuted. Let’s be clear here and I’ll try to make it simple for you. Vance has no right to things he was asking for. And they used their LEGAL rights to contest that. No matter how much you whine this is a political prosecution.
Tax fraud is criminally prosecuted all the time, especially when they don't cooperate. Leniency is for those who do more than the bare minimum, which given the extent to which Trump fought their investigation with worthless arguments, they certainly don't deserve it.
Vance certainly did have a legal right to things he was asking for. The Supreme Court excoriated Trump's pathetic legal argument.