There's this other article https://thebulletin.org/2021/05/the-origin-of-covid-did-peop... which among other things explains that gain of function is technically defined as modifying existing human viruses to make them more dangerous.
The SARS2 quite likely isn't based on an existing human virus but on a bat coronavirus.
The NIH has been apparently funding modifying bat coronaviruses in Wuhan with minimal guardrails as to be able to infect humanized lab mice but that's not gain of function as per that definition.