The flaw is that there is never any way to actually tie the real world to the Blockchain. It's literally impossible. You can have all the fancy mathematically proven Blockchain records you like, but it's just impossible to tie that to an actual tomato or actual pesticide.
We have track and trace system already for crops and they have the same problem: all the paperwork in the world can't prevent someone from, say, weighing a box of tissues instead of the box of cigars you intend to sell. In the end you need to trust someone.
I think this is a holdover of thought from bitcoin. Bitcoin wanted to be a currency for our real world economy. It never became more than that for many reasons. ETH (and now more modern chains) have become more than currencies. They are digital economies. Physical items are foreign goods in a foreign jurisdiction the local economy has little control over.
Even within crypto, different L1's are like foreign economies, and moving assets cross chain is complicated.
And how does blockchain prevent them from lying?
> you need to sign up and authenticate literally all the farm organizations in Europe, and all the competing grocers and transport companies. They all need to sign that they trust the third party service to be a fair and neutral record keeper
Instead they all need to sign up onto the blockchain and lie directly on the blockchain
> Each tomato can have its own blockchain with attested entries from each fertilization, spray, and transporter, all added and attested at the point where lying is hard
Fertilizer put on the record that tomatos are fertilized.
Sprayer put on the blockchain that tomatos were sprayed.
Transporter put on the record that tomatos were transported.
You arrive at the shop to find rotten potatoes instead.
How did blockchain help?
Also note that in this current world that is so horrible according to you you arrive at a shop to find tomatos that have passed all inspections and have been delivered to you. What eaxctly does blockchain intend to solve?
In order to solve this in a centralized way, you need to sign up and authenticate literally all the farm organizations in Europe, and all the competing grocers and transport companies. They all need to sign that they trust the third party service to be a fair and neutral record keeper... the third party company which has enormous financial incentive to cheat, on behalf of literally all its customers.
But with distributed ledgers with attestation, the record is unfalsifiable. Each tomato can have its own blockchain with attested entries from each fertilization, spray, and transporter, all added and attested at the point where lying is hard and the value of the lie is low.
You could achieve this with paper and signatures for each tomato, but it would be a lot of paper.