It peaked at 4.05% in March. The last 2 months it went just below 4% as the Unknown category increased. For June the reverse happened, so 4.04% seems to be the real current share of Linux on Desktop as desktop clients were read properly/werent spoofed.
I think Alpine uses Busybox, but it’s feasible for a Linux distro to use BSD coreutils. Not sure if any do that, though.