This is very obviously false. With the default filters with all OSs shown, Arch has 0.20% marketshare and Linux has a total of 2.29%. That means Arch is about 8.73% of all Linux systems in the survey. If you select the Linux only results, then SteamOS appears as its own entry, alongside a few others like Flatpak. We can see two things here:

• SteamOS Holo is 36.47%. This was very clearly not counted as a part of Arch Linux in the all OSs tab.
• Under these filters, Arch is even higher at 9.7%.

What's impressive here is not just the confidence with which you called the article dishonest and uninformed while not spending half a minute to check your false assumption, but also how many people upvoted you. This was trivial to prove wrong and in fact people have already done that below. Why are people so eager to believe the article is wrong that they will jump to agree with a blatantly wrong comment while having no knowledge of the situation themselves?