The way it works is that the ISP assigns the home user's router a prefix (e.g. 64 bits). Devices on the home network pick a random address within that prefix, a

The way it works is that the ISP assigns the home user's router a prefix (e.g. 64 bits). Devices on the home network pick a random address within that prefix, and regenerate it periodically, keeping the old address alive for a while too. Only the router needs an IPv6-to-MAC-address map (it always needed that, this was no different with IPv4). The ISP just has a static route that sends all traffic matching the prefix to the router. With this you can still easily recognize households by IPv6 prefix, but at least you cannot reliably distinguish devices within that household.