> If a search change demonstrably has a negative effect on company earnings (even if users like it) it will almost certainly be reversed.
This is completely false. I've personally been involved in launching ranking changes that negatively impacted revenue substantially. I didn't find out until months later through the grapevine, and only in vague terms like "ads had to scramble." Versions of them remain in production today. Revenue projections were never considered as part of the launch decision, nor have they they been consulted as part of evaluating subsequent versions.