A different airline accepting a particular test isn't "proof" that was a proper test (or any other criterion, for that matter). Admission into Thailand is proof of nothing.

Most countries (including the U.S.) generally accepted the airline's assessment. Some countries (like Germany) did not. That's not to say that it wasn't always on a case by case basis, or couldn't have changed at any given time. Any country that has a criterion reserves the right to check it if they want to.

.