This article is kinda misleading. Nearly 40% of Linux devices is the Steam Deck which is AMD only. Subtracting the Steam Deck AMD usage on Linux more or less matches that on Windows.
See the Steam hardware survey for the numbers that this blog spam article is reporting on: https://store.steampowered.com/hwsurvey/?platform=linux
Yup, 40% of that AMD share is the Steam Deck.