[philliphaydon]

It doesn't ensure that the data is correct, valid, hasn't been tampered with, or even entered.

A supply chain involves 3rd parties who have nothing to gain from this. If the issue is the middle man between A and C, blockchain isn't solving any problem. The distrust is with B, having a blockchained backed paper trail doesn't provide anything a database gives you right now.

You're asking for a single source of truth between A B and C. And saying you cannot trust A B or C, so you want blockchain to solve it, which needs to be created by someone, so you introduce D and now you have a central governing body who dictates everything for A B and C. Or you are A and you say 'hey B and C, you need to use this system we created cos we don't trust you!'.

Blockchain solves nothing in the supply chain.

[everfree]

It ensures that data hasn't been tampered with after initial entry. And that a uniquely attributable digital signature gets recorded at the point of entry, along with a timestamp.