every single satoshi is still traceable to its generation block
Bullshit. Send some coins from addresses A and B to address X and then send 1 Satoshi from address X to address Z. Did that 1 Satoshi originated from address A or address B?
Every bitcoin transaction has inputs and outputs. You can look at the transaction sending 1 satoshi to Z and see which inputs were used, and which previous transactions they were outputs from. You can trace this back to the mined coinbase transaction. The only time this gets fuzzy is if you have many inputs and outputs. For instance, if before sending to Z you merge the inputs by creating a transaction combining them into one output, and then use that output as an input to send 1 satoshi to Z.