Ecash does not remove the postgres database or any pool visibility—the pool will still have (and must have) full visibility over shares submitted because it needs to do accounting and proper payouts according to those shares. 

Share accounting is also reward accounting, so the only improvement here is we are relying on a trusted mint to be a valid custodian of the Bitcoin, not just the pool (unless the pool is the mint, which kind of defeats the purpose of the ecash because the pool still has full visibility over the share accounting).

I cannot see any additional benefit here, just an additional trusted third party…