No, they don't. They simply have to be able to articulate legal intent. What the request will almost certainly fail on is that they have to be able to also articulate why they require the tape in order to conduct oversight. "We don't believe Hurr when he says the transcript has no material difference from the tape" will not cut it.
My point is not, and never has been that the DOJ has a legal obligation to give the tape. My point is that they should give the tape on the principle that Democrats ARE willing to subject themselves to oversight as long as that oversight does not actively hamper the presidential duties. Getting reelected is not a presidential duty but a personal one.
I understand it's completely unfair to insist on playing chess while the only thing the other side wants is to simply crap on the board. And it sticks in my craw too. But the sad truth is that someone has to be a grownup, if there's any chance of ever having a working political system. Since there's only 2 options for that role and 1 of the 2 is completely uninterested that kind of limits it.