AFAIK, libfyaml[0] (not to be confused with libyaml) passes the 1.2 test suite, and if I remember correctly, it's currently the only YAML loader with that claim at the moment.
The yaml.orf website also lists a bunch of implementations, with about 1/3 supporting 1.2. I'm guessing that the users of those libraries just happily hum along and we never hear from them!
The issue is that downstream consumers of popular languages with a vocal community here on HN tend to just pull in libyaml, PyYAML being the major offender in my mind.
The tag schema used is supposed to be modifiable folks!
And why anyone would still be using 1.1 at this point is just forehead palming foolishness.