Have they ever talked about why the content isn't stored/read from ZFS just the root pool?
Single drive ZFS brings snapshots and COW, as well as bitrot detection, but for Netflix OCAs, snapshots are not used, and it's mostly read-only content, so not much use for COW, and bitrot is less of a problem with media. Yes, you may get a corrupt pixel every now and then (assuming it's not caught by the codec), but the media will be reseeded again every n days, so the problem will solve itself.
I assume they have ample redundancy in the rest of the CDN, so if a drive fails, they can simply redirect traffic to the next nearest mirror, and when a drive is eventually replaced, it will be seeded again by normal content seeding.
am I missing something or that "yet" is more like "maybe sometime if ever"?
We haven't been to the center of the galaxy yet.
We haven't achieved immortality yet.
Both are valid sentences without any fixed timeline, and in the case of the first, a date that is hundreds of thousands of years in the future at soonest.
"yet" just means "up until this time" (in conext, sometimes it means "by the time you're talking about" - e.g. I'm scheduled on-call on the 13th, but i won't be back from my PTO yet).