Mapping ::1 to 127.0.0.1
You're not actually mapping ::1 to 127.0.0.1 in this case. You're providing an invalid name for ::1 that is essentially disabling the entry. You can't map an ipv6 address to an ipv4 address - they're not compatible.

If you need localhost resolution for ipv6 to not be enabled, simply comment the ::1 line out, or don't include it at all.