Why did the WHO-China team call the lab origin hypothesis “extremely unlikely” when their “Terms of References” did not mention it at all?

Following the May 2020 World Health Assembly resolution 73.1 regarding COVID-19 (item 6 on page 6), the World Health Organization and China agreed in writing in a July 31 July 2020 document titled “WHO-convened Global Study of the Origins of SARS-CoV-2 'Terms of References for the China Part'”.  Notably, these terms of references did not even mention the hypothesis that a laboratory in Wuhan could be the origin of SARS-CoV-2.

This raises a question: Under what authority did the WHO-China joint investigation team working in Wuhan January 14-February 9, 2021 conclude that it was “extremely unlikely” that a laboratory was the origin of the virus? (https://www.youtube.com/watch?v=CaWGtKP3z4A. at 3:07:45 of 4:45:05).

When were the plans made to meet “with the staff of the Wuhan Institute of Virology and three other laboratories in Wuhan” as reported by WHO Team leader, Dr. Peter Ben Embarek, in his answer to question #4 of his interview with Science magazine’s Kai Kupferschmidt?

One clue in the chronology of events is provided by the WHO in its video interview (with transcript) with Dr. Peter Ben Embarek dated January 14, 2021 titled: "COVID-19: Origins of the SARS-CoV-2” (from minute 3:19-4:25), when he says:

"We have now the tools that allow us to look at the genetic makeup of these viruses. And when we look at our virus, the COVID-19 virus, there is nothing in its makeup that would indicate that it has been manufactured. It's clearly a natural virus and there are many of these around, we have seen several of them in the past. So, in itself it's not a surprise. Laboratory accidents happen unfortunately once in a while. It has happened many times in the past. And of course, it's even a remote possibility. We have to look at this as a possibility. So, we will of course also look at that hypothesis among many others, even if it's an unlikely one. There is no evidence so far indicating that anybody was working with this virus in the past. There is no evidence to indicate that it would have escaped a laboratory in any way, but of course we will have that in mind when we look at the origin of this virus.”

Yet the “Terms of References for the China Part” did not even mention including this hypothesis of a laboratory origin of the virus, nor did the ToRs include any mention of including team members from either WHO or China with the appropriate expertise to carry out a credible investigation of this hypothesis. So, again, under what authority was the decision made for the WHO-China team to declare at the press conference in Wuhan February 9 that it was “extremely unlikely” that SARS-CoV-2 had its origin in a laboratory?

Even the March 4 open letter  from 25 international authors “Call for a Full and Unrestricted International Forensic Investigation into the Origins of COVID-19” does not note the fact that the WHO-China Terms of Reference makes no mention of investigating the laboratory origin hypothesis of SARS-CoV-2.