If you don't have mining, or a similar way to decide between various possible forks, what you have is a cryptographically secured append-only ledger (such as what the git data-format resembles).
That's not a blockchain and that idea has existed for decades already.
I think that idea is now being called a "blockchain" since in reality the trustless/proof-of-work nature of a true blockchain is largely wasted for specific companies.
It's not a redefinition, it's a definition that has been around since the 1990's [0], the only requirement for a blockchain is A) directed linked list (block points to previous block) and B) cryptographic security (use hashes as block index)
Bitcoin is merely the first application to use Blockchain in a decentralized proof-of-work manner.
It is a blockchain is you don't merge since you have a commit pointing at a previous commit, (block points to block), merges point to two parents but Ethereum has that almost with uncle blocks.
The commit log of a repo is almost certainly a blockchain, which is why I mentioned "to some extend"
That's not a blockchain and that idea has existed for decades already.
I think that idea is now being called a "blockchain" since in reality the trustless/proof-of-work nature of a true blockchain is largely wasted for specific companies.