Here in Australia, Nielsen is the endorsed measurement.
Nielsen has three settings. 0-seconds (BTR). 2-seconds (IAB endorsed), and 30-seconds (a comparative to TV and for long-form content).
We have switched the interfaces to 2-seconds as the default, 30-seconds is an interface option and that 0-seconds no longer appears (though the IAB Measurement Council can see the data for research analytical purposes). I can see a time once 2-seconds is embedded that 0-seconds will disappear completely.