It can be quite useful for a more complex ledger between multiple banks. Yes it’s not open like Bitcoin but it’s easy to connect multiple partners, provides immutability / transparency, deals with varied levels of trust between actors (banks, shipping companies, importers / exporters, government entities), and allows you to formalise trade finance rules in a smart contract, etc without imposing a central database / solution. It’s an closed network involving complex transactions between a range of parties and therefore blockchain / smart contracts is actually a good solution.