The 7.4-stable branch was created some time ago with changes that were intended to be released in 7.4. Since the branch was created, we have added feature flags for all potentially incompatible changes, but these feature flags were added in master and do not exist in 7.4-stable. In order to release 7.4, the feature flags and associated documentation need to be backported to 7.4. This will take more effort than simply cherry-picking the relevant commits because the 7.4 feature flags were mixed with 7.5/8.0 feature flags - some conflicts would also need to be resolved.