In SERVER-83754, we made changes to how the registration macros (like REGISTER_DOCUMENT_SOURCE_WITH_FEATURE_FLAG) handle feature-flag/FCV checks. However, we missed that some of the logic is inconsistent across different registration macros. For example, we unconditionally register every single document source (here) and then check FF on parsing, whereas we conditionally register accumulators (here).

We should audit all the registration macros to have consistent behavior. They should probably follow the example of document sources, where we always register them, in order to properly handle upgrade/downgrade.