IPv6 prefix from T-Mobile USA used but not announced in BGP (2607:7700::/32)

Hi, While doing statistics on the participants of a public DHT, I was surprised to see some IP addresses that are not present in the DFZ: 2607:7700:0:25::4e00:605b 2607:7700:0:25::4e25:8ce8 2607:7700:0:25::c808:db2c 2607:7700:0:4::3294:6683 2607:7700:0:4::4c09:4d39 2607:7700:0:4::5985:87d1 2607:7700:0:4::5d7d:3df8 All those IP are in 2607:7700::/32, allocated to T-Mobile USA but never announced: https://stat.ripe.net/2607%3A7700%3A%3A%2F32#tabId=at-a-glance What could explain their usage in an application? Some form of address translation? Maybe these addresses have been used as source address in outgoing packets, which would indicate IPv6 tests in T-Mobile? (but obviously, nobody is able to answer such packets). Baptiste