I can’t link to an absence of a thing. I looked through his link and I didn’t see any mention of gain of function research. Maybe I missed it because that thread is completely schizophrenic, but I did look.
And yes, he does talk about gain-of-function. His background is in high risk biocontainment viruses, and his PhD was specifically focused on Ebola-, Hanta-, and Flavi-viruses.