Most jstests only insert a few documents, meaning the CBR fallback is not reached by most tests even though it is on by default. This includes passthrough suites, which are essential to testing the variety of scenarios that the optimizer could run in.

To trigger the CBR fallback more, a failpoint could be added here so the fallback is triggered when the failpoint is enabled. This would not be set by default. Instead it could be set in the allFeatureFlags variants, so that all passthroughs would use CBR fallback