So if one ignores the liability/regulation part of this stunt, and just look at the technical merit. Could you then say that this blockchain really provides nothing that a traditional centralized system wouldn't? But at much higher complexity and cost?

Wouldn't that just mean that the whole schtick is to avoid regulation? If I as a regulator saw this, I'd just schedule it for my next meeting, since you want to avoid having companies doing regulatory exploits "until regulation catches up". It's Uber all over otherwise.

> Could you then say that this blockchain really provides nothing that a traditional centralized system wouldn't?

Blockchains (in general) enforce not only open code, but open data.

Technically, nothing prevents traditional banks to offer standardized easy-to-use and easy-to-onboard API access to their financial data, but in reality incentives are not there (quite the opposite).

Blockchains are a contrived way to enforce open code and open data. There are other technical ways to do that, but none of them has been found to actually work in reality.