That comment is about the semantics of OS APIs; filesystems are designed not to corrupt themselves in case of hard shutdown, and this is true as long as the underlying storage is well-behaved (e.g. honors flush requests). Databases on macOS already use F_FULLFSYNC (if they noticed this issue) to provide those guarantees. On Linux they just use fsync().
That comment is about the semantics of OS APIs; filesystems are designed not to corrupt themselves in case of hard shutdown, and this is true as long as the underlying storage is well-behaved (e.g. honors flush requests). Databases on macOS already use F_FULLFSYNC (if they noticed this issue) to provide those guarantees. On Linux they just use fsync().