Why does R show a different version of the OS than what is installed?
According to ?sessionInfo
Where R is compiled under an earlier version of macOS (as the CRAN distribution has been) but running under ‘Big Sur’, macOS reports itself as 10.16 (which R recognizes as ‘Big Sur’) and not 11.x.
osVersion
#[1] "macOS Big Sur 10.16"
sessionInfo()$running
#[1] "macOS Big Sur 10.16"