So which of the 5 UTXOs went to which person? You don't know that unless it gets moved back to a known address later.
> gets moved back to a known address
"spent", in the Common Tongue
This might be your logical mistake: there is no 'known address'. CashShuffle is based on HD wallets that generate billions of addresses. No reused addresses. No circles in the graph.
Spent is from the transmitter's perspective. Coins aren't destroyed, they are just moved around.
If I send all my coins to an unused address of mine, there's no way to tell if that is me or another person. If later I send them back to the address that was known to be me...
Then you know I have them, but you still don't know if I sent them back there, or some other party did.
You are thinking that, since it's easy to list all the possible chess moves in the next move, that you can tell for sure how the board got in its current state after 100 moves.
