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 the venn diagram overlap of linux users, and users of adblockers or noscript users that block such tracking is quite large. Must impact the statistic significantly.
I use ad blocker but do not spoof user agent. If uBlpck does not block statcounter, I should be counted.