So this change:

[BUG] pruning: grid: add all snapshots that do not match the regex to the rule’s destroy list. This brings the implementation in line with the docs.

I've been unknowingly relying on the "bug" to have the job only prune snapshots with specified regex in type grid like so:

- name: snap_hourly
  type: snap
  filesystems: {
    "<": true,
  }
  snapshotting:
    type: periodic
    prefix: zrepl_hourly_
    interval: 30m
  pruning:
    keep:
    - type: grid
      regex: "^zrepl_hourly_.*"
      grid: 1x1h(keep=all) | 72x1h
- name: snap_daily
  type: snap
  filesystems: {
    "<": true,
    "mypool/downloads": false,
  }
  snapshotting:
    type: periodic
    prefix: zrepl_daily_
    interval: 10h
  pruning:
    keep:
    - type: grid
      regex: "^zrepl_daily_.*"
      grid: 30x1d

And that seemingly innocent "[bug]" tag changelog managed to clear up my entire snapshots 🙃