Which is the main argument against this kind of function research - there’s little gain compared to the risk.
“We will introduce appropriate human-specific cleavage sites and evaluate growth potential in [a type of mammalian cell commonly used in microbiology] and HAE cultures,”
They were denied over Gain of Function concerns, and bam a year later the only Sars virus to be ever observed with those exact human-specific cleavage sites at the S1 S2 junction ravages the planet starting 500m from WIV.
https://theintercept.com/2021/09/23/coronavirus-research-gra...
But the preponderance of evidence is that the leaked virus was modified before it was leaked. The critical spike protein in SARS_CoV2 is coded uses a sequence of amino acids that has never been seen before in any other coronavirus. I forget the names, but there are certain common amino acids that can be coded using several different functionally-identical DNA (RNA) sequences, and the SARS-CoV2 one looks like the sequences used in labs and humans, and never seen before in natural viruses. One nobel laureate in biology described this as a "smoking gun" that this was a lab leak when they first heard about it.