I just found out that, while the above is true, there is a difference in behaviour between notes and static pages:
Notes *do* become searchable again after they've been edited (and thus reindexed within 30 seconds).
Static pages, OTOH, *don't* ever become searchable when edited and rescanned (even though being reindexed within 30 seconds).
(I.e., the "search_observer_queue" table gets its "UPDATE" directives to the search_indexer inserted in both cases)
BTW, it was only yesterday that static pages at all became searchable *after having been updated*. See: this thread.
So... to reiterate, my current worry is reviving searchability of static pages after the dropping-and-recreating of the openfts-driver, in case I didn't make myself clear😉
