Some more details... While IPv6 should be preferred, 6to4 turned out to not work so great in practice. So it's a good decision by Apple to prefer IPv4 over it.

Some more details... While IPv6 should be preferred, 6to4 turned out to not work so great in practice. So it's a good decision by Apple to prefer IPv4 over it. But other kinds of IPv6 connectivity (including native) should still be preferred over IPv4.