Codon usage changes naturally in viruses, including in SARS-Cov2. Strong preference isn't an absolute https://www.sciencedirect.com/science/article/pii/S0042682222000186?casa_token=O9xG3w4PuzEAAAAA:DOkygd727KXfP1hlHe2b8CnlXOpjs3bK1m0as9BfieCCmfedYzAot9O_c6nAQvbxtpfHs5PELw As for the supposed "smoking gun", the Furin cleavage site..., the title of the linked paper is SARS-CoV-2 furin cleavage site was not engineered https://www.pnas.org/doi/10.1073/pnas.2211107119