Comment # 1 on bug 1180497 from Thorsten Kukuk

The developers are not correct, using two different names for 127.0.0.1 and ::1
will break most dual-stack applications or IPv6 only installations, as
localhost would suddenly no longer be reachable.

All linux distributions I'm aware of have something like this:

127.0.0.1   localhost ...
::1         localhost ...


It is quite common that names resolve to an IPv4 and an IPv6 address (or even
multiple ones).

To me it looks more like they don't expect that a hostname can resolve to more
than an IP address and that they need to adjust their code.