At this point, about 25% of traffic on dual-stack ISPs is v4. So no, v4 isn't where all the stuff the phone wants is.

CGNAT is generally only done for v4. v6 isn't needed to provide CGNATed v4, and if v6 is provided as well then it generally isn't NATed. I expect you could find an ISP somewhere that NATs the v6 too as a counter-example if you looked hard enough, but as a rule they don't.

(Sometimes CGNATed v4 is provided by making use of the v6 in some way -- e.g. mapping v4 destinations into v6 with NAT64, or by tunnels -- but the CGNATing still only applies to v4 destinations, so this just an implementation detail rather than an undermining of the above point.)

> Cgnat you are restricted to tail scale stuff.

But only on v4, not on v6. That's kind of the point of bothering to make v6 in the first place -- it allows you to keep the ability to poke holes in your inbound firewall even in a world where v4 is exhausted to the point of CGNAT.

The exhaustion and the CGNAT and the resulting restrictions would still be there if you didn't have v6. It's just providing you with a way out of them.