Alta AP/ssid IPv6 ULA

What is the IPv6 address that is being assigned to my iOS devices when connecting to an Alta AP/ssid? It starts with fdae:db55:fb50:ea4d. This does not happen when I use the same iOS devices and connect to a Unifi AP/ssid. Appears to be a ULA, but why is it only being seen when connected to an Alta AP/ssid? IPv6 is not enabled within local network, so the Alta APs must be generating something that is triggering this. This is more of a “why is this happening” rather than an issue.

Appears this may be Thread protocol related to AppleTV and HomePod devices advertising ULA ipv6 network. Within the same subnet, this behavior can be seen. On other subnets where the devices are not present, this doesn’t occur.