This came up while working on SERVER-97917 after SERVER-94660 was merged. Using featureFlagRankFusionBasic (which isn't FCV-gated) in api_version_pipeline_stages.js would make the test fail in the sharding_jscore_passthrough_last_lts_new_old_old_new suite. This is because FeatureFlagUtil.getStatus() would not be satisfied with the response from mongos and would try to check mongod instead, and the mongod with the response was on a version with the FF on, prompting a false positive.

will.buerger@mongodb.com attempted patching the behavior for not doing this redundant check on non-FCV-gated flags, but this then prompted an error with ftdc_connection_reuse.js since it relies on creating a new connection, but for with the above-mentioned patch we wouldn't get to that block of code. To fix this we can create a new connection inside hasMultiserviceFTDCSchema().

This will allow us to switch the unstable pipeline in api_version_pipeline_stages.js to be guarded under featureFlagRankFusionBasic.

Note that aggr_operationstats.js might also fail but this should be fixed by passing conn instead of standaloneColl into the FeatureFlag helper.

Also, we might want to schedule a ticket for Catalogue and Routing for them to verify whether they want to keep our fix or clean it up in a smarter way.