I haven't run the windows wallet in a while, and I don't remember what my cpu usage for the wallet was. But on my raspberry pi it's usage is sitting around 0.4%. So if the windows wallet uses so much cpu and the linux wallet uses next to none, this leaves me to believe that the gui is what is eating away at the cpu. So if the wallet auto starts in the background (no gui), and the gui only shows when the user requests it, then there wouldn't be any issues?
or perhaps, the wallet is just much better optimized for linux. In which case, the windows wallet should probably get an optimization pass.
No the user must have a specific problem, the Windows GUI wallet uses a tiny amount of CPU on my Windows machine (i7-6700k) around 0-1%, it might use a lot more while syncing the blockchain, but then it will sync faster than a Pi ever could (I havea Pi too).
EDIT: Bear in mind it fluctuates all the time simetimes higher, sometimes lower.