If you have the latest PS with ACR, you are correct - perhaps you don't need LR6/CC.
But, logic dictates that if you have the latest PS+ACR, then you must have CC, and if you have CC, and have "upgraded" to the latest PS+ACR, then why wouldn't you upgrade to LR CC as well and get all the things you've listed all in one package rather than having to go back and forth between LR and PS+ACR?!?
IOW, wouldn't it be a time savings simply to upgrade LR CC? Or am I missing something?