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You're right the right text should be: Let’s suppose a customer provisioned in the first stage with the prefix 2001:db8:1111::/48. Their devices are using, for our example, the first free /64 (2001:db8:1111:1::/64). Everything is fine until there is a power outage. The CPE boots up again when power is recovered, and because the ISP is using a non-persistent prefix, a new prefix is assigned (2001:db8:2222::/48), so now the CPE is announcing 2001:db8:2222:1::/64. However, the devices that have battery (laptops, tablets, smartphones) still have the previous prefix, so now they have two different prefixes (2001:db8:1111:1::/64 and 2001:db8:2222:1::/64). These devices will try to keep using the older one, and they will not work, as the ISP is no longer routing the first prefix to that customer. Just think: if another network failure or power outage were to happen now. Devices could then have three or even more prefixes. And the user will end up calling the ISP help-desk for troubleshooting because the network is not working. Regarding privacy, at the end the best way someone willing to track you has is apps fingerprinting and correlating data, not just addresses. Because the "tracker" can not be sure that it is the same "person" even if the address is the same, it may be several users in the same computer, it may be different computers using the same address at different times, etc.