Not all ISPs offer this functionality. I can’t realistically tell the customers I manage that we can’t support their preferred provider because of this, when they rightly point out that it just works on IPv4 without need for multi-homing.

And again, multi-homing does not address load balancing / policy based routing with active active links. Eg it’s possible to have 2 Ethernet connections, 1 VDSL connection and a LTE link. Can multi-homing IPv6 work in such a situation while providing fast failover and load balancing by service/application/policy?