Because the Mk3 flaw doesn’t produce selective sweeps. If a seed was weak, every UTXO derived from that seed is equally vulnerable. The attacker doesn’t “choose” one.... they can sweep the entire wallet deterministically. When only a single UTXO moves and others remain untouched, that’s the signature of a different failure path: partial key exposure, a compromised backup, a reused seed, or an external leak. The Mk3 randomness bug doesn’t create that pattern.