this search result should contain the pages "Wikipedia:Village pump (technical)/Archive 2" and "Wikipedia:Village pump (technical)/Archive 9", but doesn't do so. I've checked their histories and logs and can't find anything out of the ordinary.
According to https://en.wikipedia.org/w/api.php?action=query&format=json&prop=cirrusbuilddoc%7Ccirrusdoc&titles=Wikipedia%3AVillage_pump_(technical)%2FArchive_9&formatversion=2 the create_timestamp field is not yet present in the index. I suspect our reindex process to have missed this page since I believe we waited for 2 month before announcing that this new field was available (2 month being the time we estimate a full refresh to take).
We'll have to investigate the logs to determine what happened but since it's a 2 month process clues may be hard to find.
Kind of good news / bad news. The good news is the patch is merged and will deploy this week. The bad news is the bug was in the process that backfill's old properties like the somewhat recently added page creation date. It's basically going to take 2 more months before these new property sorts take into account all pages.
Checked current query, as expected (it hasn't been two full months yet) there are still ~7 pages that match the example query that have not yet been reindexed, Expecting these 7 to be reindexed sometime in the next 4-5 weeks.