You should have a look at the IPv6 privacy extensions. IPv6 doesn't work as you think it does. Your devices use temporary IPs even with a static IPv6 prefix.
Most ISPs give you a new prefix occasionally, such as every night. They don't need to, but so many do it anyway that a tracker cannot assume that 2001:a61:2574:a00/64 is the same customer as yesterday. It may be the same, usually isn't, so tracking is very imprecise.
Often, in order to allow customers to use multiple subnets, ISPs will allocate a /56 (256 subnets) to customers.
For privacy purposes these have the same behavior as IPv4 addresses, in that they in theory can be rotated between users but in practice have lifetimes on the order of months.