It's not perfect for the largest whale in the pool, but this imperfection can be mitigated by waiting for remixes. During the 4 days that it took for the 137 BTC input to decompose, hundreds of new BTC entered the pool and thousands of old BTC remixed. Even if 137 BTC was spent in a future consolidation, it could have come from a different origin (such as 137 separate 1 BTC inputs from another user). Maybe this still doesn't meet your "practical" standard, but this edge case scenario only affects a single user.