But you wouldn't be able to meaningfully audit a retail bank at all by looking at the ledger, because meaningfully auditing a retail bank involves understanding

But you wouldn't be able to meaningfully audit a retail bank at all by looking at the ledger, because meaningfully auditing a retail bank involves understanding their loan portfolio (in particular whether the entities loaned to are likely to default more than predicted in future and whether assets loans are secured against retain their value). You're not going to get all that from a transaction ledger, and particularly not one designed with privacy in mind Simply knowing how many reserves the bank holds gives you no indication whatsoever of its solvency.