[NoZebra120vClip]

Couple things here:

The GP describes resolver software, which corresponds to item 6.3.3, not a caching server. This does specify the same behavior.

In RFC terminology, "MUST" > "SHOULD" > "MAY", so there is some wiggle room there.

6.3.2 permits Chromium and other apps to hardcode localhost names as such, instead of using a resolver.

A very popular vector for adware/malware is to take over the system resolver, or replace the DNS client configuration, so this is one reason Chromium jealously guards 127.0.0.0/8