@sun @feld and it's not a priori unlikely that it did

> Our analysis exhibits furin cleavage sites at spike S1/S2 occurred
independently for several times in coronavirus. Consequently, natural
occurring of the site in SARS-CoV-2 is highly possible https://pmc.ncbi.nlm.nih.gov/articles/PMC7836551/pdf/main.pdf

that's even though covid was the only virus in its branch that has the adaptation