Why does Kaspa's ATAN design start archiving from a pruning point?

Kaspa's ATAN starts recording from a pruning point — a specific past block that any full Kaspa node can independently recognize — so that new nodes joining later have a verifiable anchor they can check without trusting the archiving node. Instead of storing data from the very beginning of the chain, the ATAN begins at the most recent pruning point P for which either all L2 transactions fall in P's future, or some commitment to the L2 state at that point already exists. A new node receiving data from a synced ATAN can simply ask its own Kaspa full node whether that pruning point is legitimate before accepting any transaction history that follows it. For anyone building on top of Kaspa — such as an L2 network — this design provides a trustworthy starting place for transaction data without requiring blind trust in a single archiving source.