The query I shared is limited to changes on site settings and limited to actions by system. So it helps noticing when settings are changed by system either because of an automation, like disabling image download because of a full disk or the setting changes when bootstrap mode ends. In combination with a post or PM by the automation plugin this can help in cases like the one described in the OP.
But the query doesn’t really help to find unexpected changes like the change that disabled the welcome message of discobot @gassim would have liked to know about. Most setting changes that happen during a Discourse update aren’t logged and that’s what makes them so hard to track down.