Currently, aggregation_ifr_flag_propagation.js doesn't validate that the vector search IFR flag value reaches the shard as it promises to. This is because when $vectorSearch appears on the router, it gets desugared into $_extensionVectorSearch and sent to the shard if the flag is enabled. The shard never checks the value of gFeatureFlagVectorSearch because it doesn't have to, it received $_extensionVectorSearch not $vectorSearch.

When the flag is off, $vectorSearch uses the fallback parser on the router and fails with SearchNotEnabled. In both cases, the shard's flag value is irrelevant to the test outcome.

This ticket should alter this test to somehow check the value of the IFR flag sent to the shard.