Apple's apps bypass firewalls like LittleSnitch and LuLu on macOS Big Sur

A great example of why you need defense in depth. Ideally you'd be running the local firewall on your box, as well as an external firewall.

That being said, this is not ok behavior on Apple's part. There shouldn't be a way for traffic to go around the firewall like this, even if it is just Apple apps.

Because as Apple well knows, once you make a backdoor, someone will figure out a way to exploit it.

If you're on a laptop, you won't necessarily always be able to filter on the router level.

Of course not, which is why this still isn't very cool. If you're super paranoid you can always carry around a small router or a pi to attach to the wifi and be your external router though.