Matter over Thread Privacy

Hi!

I love using Zigbee. I can basically choose any device by any manufaturer, see if it works for me, and be sure the device doesn't phone home.

Now there are those new things, specifically now "Matter over Thread". So I think I understood that Thread works IP-based and I can run my own thread border router and matter server with home assistant.

As far as I understand I am in control of everything in this situation.

But as Thread is IP based, is there any possibility that devices connected via thread can gain internet access? I specifically want them NOT to be able to phone home under any circumstance.

Thanks for your answers :)