That's arguably
not the most interesting architectural aspect of Git.
Or does any back-linked tree data-structure becomes interesting if the nodes keep a hash of their parent instead of a raw reference? I don't think that's the case.
It might be a bit heretical but I don't think Git has a super interesting internal architecture. I'm not downplaying the fact that Git was very innovative, especially considered the landscape of SVMs at the time. The tool as a whole is great and has desirable properties but its internals don't strike me as particularly innovative. It's a clever composition of solutions to well established problem domains. And in that aspect it is a beautiful engineering solution although there is room for a lot of improvement in terms of UX.
And in addition to that, I would argue that it would be a very weak definition of "blockchain". The innovation in Bitcoin is the incorporation of proof-of-work and resulting alignment of incentives such that it can achieve probabilistic consensus in an adverse setting and with some degree of asynchronicity.
The underlying structure of the data is an obvious choice because it is simple and "captures" the idea of aggregate global state, but it's also hardly an important innovation. UTXOs are more significant.
And also, recall that the textbook example for state-machine replication is always an append-only log for example. So that's not the crux of it, or of blockchain, in my humble opinion.