Currently, fetching indexes as part of getting routing information from the catalog cache is not feature flagged since the mongos does not have a concept of FCV. However, we are seeing a performance impact of fetching the global index information when a collection is accessed by a mongos for the first time.

This ticket is to feature flag the fetch of index information based on the binary. It's not a perfect solution since once the feature flag is enabled, we will still have the performance hit without global indexes, but this will prevent there being a performance hit in upcoming releases while SERVER-72323 will come up with a better solution.