Hash trees are used in the IPFS, Btrfs and ZFS file systems, BitTorrent protocol, Dat protocol, Apache Wave protocol, Git and Mercurial distributed revision control systems, the Tahoe-LAFS backup system, the Bitcoin and Ethereum peer-to-peer networks, the Certificate Transparency framework, and a number of NoSQL systems like Apache Cassandra, Riak and Dynamo.
A Git history is a DAG[0] (each commit can have multiple parents) and beyond that a polytree (it can have multiple roots); while a blockchain is an arborescence[2] (there's a single root — the "genesis block"; and each block can only have a single parent).
Further, beyond the technicalities blockchains are generally very linear (the side-chains tend to be pretty short, forks aside) while Git repositories can be extremely broad (have lots of concurrent branches).
[0] https://en.wikipedia.org/wiki/Directed_acyclic_graph
[1] https://en.wikipedia.org/wiki/Polytree
[2] https://en.wikipedia.org/wiki/Arborescence_(graph_theory)
The answer depends entirely on definition. What properties of bitcoin are essential to a blockchan vs which properties are simply how bitcoin happens to use a blockchain?
If blockchain just means the Merkle tree, then yes.
If it means Merkle tree + a computational consensus system for adding nodes, then no.
Git also uses a Merkle-DAG, but it is not a blockchain.
If you squint, that's kind of true for Git repositories, too.
The version with the most "proof of work" on it is likely the master branch.
Of course the incentives are very different... but still, the similarity is somewhat illuminating, I think.