That's a good point that I hadn't remembered (first-class locks weren't totally baked back then), but I think the intent of my original comment holds true: we should have valued the Jepson test suite more and continuously leveraged and improved our usage of it, rather than doing one-off tests every now and then. As a result, the community has no idea if there were regressions between now and then. I will admit what I don't know: I have no idea if this was actually feasible or desirable for us or you at the time, but I'd feel more comfortable if every release of etcd, Zookeeper, etc... had some kind of Jepson stamp of approval on it in terms of API coverage. I'm pretty sure CockroachDB has tried this[0], but it's been a few years and I don't know how it turned out for them long term.
[0]: https://www.cockroachlabs.com/blog/diy-jepsen-testing-cockro...