My guess is - You only show the very corner of the card originally, the rest of the card is obscured and not correct. The 'holder' has a fake corner already added.
I bet almost nobody grasps how strong this is... So clean, so simple, so magical... Yoo are a badass Jeki...it's you & David Blaine are the 2 most amazing men alive today...
It is the 2 and the A that changes, and has to change. It explaines some. There are some methods for doing that, but I dont want to go further in case im embarrassing my self😅
Is it like how those holographic cards show a diff thing when they hit light a certain way? He always had cards at a angle when he showed us but when they were in holders they were straight up?
Look at what you see when he originally shows you the 3 cards. You only see the corner of two of them. Those corners are hidden by cut outs of the other cards when he puts them in the slots