I think the only meaningful definition of the term "blockchain" requires the idea of mining blocks / addressing double-spend somehow. Otherwise it's just a chai

I think the only meaningful definition of the term "blockchain" requires the idea of mining blocks / addressing double-spend somehow. Otherwise it's just a chain, a data structure we've had for decades. The term was introduced with Nakamoto's paper, and the insight of that paper was mining / proof-of-work, not hash chains. It is technically true that one application of blockchains is solving problems that can be solved by regular chains, just like it is technically true that one application of self-driving cars is the ability to turn off the automation and let a human drive. But if someone asks about the applications of self-driving cars and you say "Driving on the open road is fun," I think most people would not accept that as answering the question asked. (And I'm not just being pedantic: blockchains have a significant computational/environmental cost, so if you don't need the block mining feature, you will get many orders of magnitude faster performance and run many of orders of magnitude cheaper and cause fewer negative externalities if you just use a plain old hash chain.)