> "our SREs and management promise to not change anything"
But you can lock a database down to the point where only external auditors have access to the admin keys. It would make debugging challenging for sure, but that's anyway a tricky part of distributed systems such as bitcoin.
I agree that databases on their own are never tamper resistant. But you can certainly set up a process around the database that guarantees tamper resistance. You'll still have to trust said process, and with blockchain you still have to trust the code. You'll never get away from having to trust _something_, but at least it is in theory feasible to have tamper resistance both with a centralised database and with a blockchain.
With git, you have to manually resolve merge conflicts.
With blockchain, the general point is to use PoW (or something equivalent) to automatically do a vote on which is the correct version. Isn't that also the case in a private blockchain?