My Android phone gets an IPv6 address from t-mobile... but no routing / 2019-07-26

I just noticed in Network Info II that my android phone does get an IPv6 address from t-mobile. The address is something like 2a02:498:1fe1:9a02:2:3:xxxx:xxxx which is indeed in IPv6 address space allocated to T-Mobile Netherlands.

% Information related to '2a02:498::/29'

inet6num:       2a02:498::/29
netname:        NL-T-MOBILE-20080609
country:        NL

So I tested directly whether I could make an IPv6 connection to my website, but it fell back to IPv4. Network Info II saw no IPv6 route on the phone, but in later checking I also saw no IPv6 route when connected to the wifi at home, where IPv6 works fine. And doing a traceroute to that address from home shows that a core router at xs4all says network unreachable:

 3  0.ae22.xr4.1d12.xs4all.net (2001:888:1:4032::1)  6.105 ms !N  6.063 ms !N *

So T-Mobile has activated some IPv6 address management in their network, but stopped at that point.