See
https://news.ycombinator.com/item?id=45681136. The actual DNS mutation API does, effectively, CAS. They had multiple unsynchronized writers who raced without logical constraints or ordering to teh changes. Without thinking much they _might_ have been able to implement something like a vector either through updating the zone serial or another "sentinel record" that was always used for ChangeRRSets affecting that label/zone; like a TXT record containing a serialized change set number or a "checksum" of the old + new state.
Im guessing the "plans" aspect skipped that and they were just applying intended state, without trying serialize them. And last-write-wins, until it doesnt.