Thanks @monica and @seth. That's the thing, a query is generated against the index, even from an advanced search form with a single box for created date/time:
2025-05-27 10:25:16 - INFO --> [205::250240] {"query":"\n\t\t\t\t\tSELECT swi.index_id, swi.row_id, swi.boost, swi.field_index\n\t\t\t\t\tFROM ca_sql_search_word_index swi\n\t\t\t\t\tINNER JOIN ca_sql_search_words AS sw ON sw.word_id = swi.word_id\n\t\t\t\t\tWHERE\n\t\t\t\t\t\tswi.table_num = 57 AND sw.word = 'created2025-05-26'\n\t\t\t\t\t\t\n\t\t\t\t\t\t \n\t\t\t\t","params":[57,"created2025-05-26"]}
2025-05-27 10:25:16 - INFO --> [205::250240] {"time":0.0005,"numRows":0}
[Same thing for modified.] Note that there are some queries against the change_log tables, although on logged_table_num 94. On the other hand the target object histories report correct creation (and modification) times, so the change_log itself does not look suspect.
Maybe this is incidental and a red herring?