There was a recent decision to aim to allow nodes that lost 2% of data to operate. However as far as I understand, it has not yet been implemented, and the current way of computing the audit score depends on luck a lot.
From my experience, though I admit I didn’t have many opportunities to pick files out of lost+found, the chance for these files being complete is fairly high. Unless the drive is almost completely dead, metadata and data failures don’t seem to be very correlated, and files end up in lost+found if their metadata is corrupted.