I think it's important to point out that the percentages are not necessarily that meaningful. If more people are using steam deck and ditch their windows PCs for it, it's not an OS choice. It's a choice to move to consoles. Additionally, steam deck also competes with traditional console brands (PS, Xbox, switch) and might take some market share there as well, so that even if no one ditched their windows PCs, the total number of users using goes up and hence, the percentage.

I haven't had a steam deck in my hands, but I guess that it doesn't need the user to understand the underlying system at all. It can be used by the same unskilled people who use android or iPhone. So, one core requirement I think people need to have to install any other os is not met or even trained, which is actual knowledge about computers.

The reports about "increase in market share of Linux user's" is from my point of view, which is "I think it would be great if people would ditch windows and office" just a market bit. Useful but ultimately little meaningful.