It simply means that those features are not implemented yet. As chrfr correctly notes, Filevault will be unnecessary with APFS. Fusion Drive should work with APFS without any issues (once the support is added). Time Machine will most likely work much better with APFS than it currently works with HFS+, because APFS supports incremental snapshots on filesystem level, where HFS+ has to emulate them with hard links and copies. Practically, this would mean faster and more reliable TM backups. They could even potentially do some interesting meta-level stuff, where they do snapshots on the local disk first, then synchronise the FS tables with the backup destination, resulting in very fast versioned FS mirrors.