The fcv_upgrade_succeeds_with_buckets_without_timeseries_options.js test verifies that setFCV succeeds even an system.buckets collection without timeseries options exists. The rationale is that even through those inconsistent collections can no longer be created in MongoDB 8.0+, customers may still inherit them from previous versions.

In FCV 9.0 we added further guardrails to disallow creation of system.buckets collections:

• SERVER-114496 Forbid all operations targeting legacy timeseries buckets collections
• SERVER-123928 Forbid creation of mismatched timeseries collections based on featureFlagCreateViewlessTimeseriesCollections

However the test case is still valid (customers could still inherit those collections from v7.0 or older versions, and setFCV should still succeed) so we should find a way to keep this test even after FCV 9.0 is last LTS.