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.
Fwiw, my blog’s statistics say Linux is around 10% and I know a lot of browsers identify themselves as running on Windows when they’re not, so I wonder how it’s measured.