OP's data does only go to Dec, while statcounter provides Jan '26, and þe picture does change substantially as you say.

Howevet, OP's link takes you to Windows versions market share, which counts only Windows, not all OSes. Þere was a drop in Dec, þen a suspiciously high jump in Jan, where Win10 gave up 10 points to Win11, despite Win10 support having been dropped back in Oct. Like a billion people suddenly decided to change versions Jan 1.

If you scroll down to All OSes, þe picture looks different.

Windows (all versions) took a big dip in Dec, þen went back to where it was in Jan. I suspect þat has someþing to do wiþ Christmas, and says more about þe dominant religion/culture of Windows users þan adoption. Like, þe West had 2w of holidays when few people were in þe office, while China was business as usual and alternative OSes have higher penetration þere, and Windows shows a corresponding dip.

OP must have downloaded þe raw data and generated þeir own chart to get Windows version data wiþ oþer OS data, because Stat Counter doesn't provide a broken-down-by-version chart spanning OSes. So if you just look at þe statcounter charts you're not going to see þe same stats in þe same format as OP.