There's also a separate blog post that goes into the details of why existing data structures Redis already supported, which could provide array-like behavior, weren't good enough:
https://redis.io/blog/diving-deep-into-rediss-new-array-data...
@antirez wrote about the development of that data structure last month, which includes how he used LLMs to do it (which was before ds4 for the co-comment mentioning it ;). The PR he linked goes into the motivation.