>Furin cleavage sites are not common in other related coronaviruses.
However, this claim appears to have been investigated and debunked [1]
>Furin cleavage sites occurred independently for multiple times in the evolution of the coronavirus family, supporting the natural occurring hypothesis of SARS-CoV-2.
[1] https://www.sciencedirect.com/science/article/pii/S187350612...