In 7.0, we implemented version 2 of the queryable encryption protocol, which reuses a lot of the logic written for the preview version. To maximize code reuse, instead of having separate code for the v2 path, we instead check the feature flag in multiple areas of the QE code base in order to branch the v2 code path off of the v1 path. This creates a problem with respect to FCVs, because the FCV can change and affect the value of the feature flag, while in the middle of an operation.