As stated, it's a proof of concept. The trust element was between the user and the software provider. 'How does a user trust that the software provider doesn'

As stated, it's a proof of concept. The trust element was between the user and the software provider. 'How does a user trust that the software provider doesn't make changes to user data without the knowledge of the user'. In this case, making changes to the audit history and/or invoice data. While this is unlikely, it's possible. And the point of the blockchain in this case is to make it impossible, at least without being noticeable. While that doesn't sound all that amazing by itself, it does enable some interesting use cases to be built on top. Now that the data has been made trustless, and verifiable by 3rd parties it could be provided to parties such as: Government, Accountants, Lenders, Banks, etc. Regarding fake data, sure, you can submit fake data. But when an audit occurs, you need to submit your fake data to be audited. What you can't do, is go back and change the numbers.