Not sure why they downvoted you because you have a point - icons are not the same as Windows XP's, wallpaper flat color reminds me more of Win 95/98 and the taskbar design has some details that do not match precisely with Windows XP's. I'd also bet it's due to copyright concerns
Probably cos it's vibe coded?
The main CSS comes from XP.css [0], but the AI additions [1] have definitely messed it up in some way.
The whole thing is pure JS which is nice but the comments give a good impression isn't not hand written IMO [2]
[0]: https://github.com/botoxparty/XP.css/
[1]: https://explorer.samismith.com/css/base.css
[2]: https://explorer.samismith.com/js/explorer.js