They do sell some PCs, but their market share is very low, and I can't imagine it's a significant part of their revenue. They definitely wouldn't bother slowing down Windows 11 adoption to sell a few more Surface Books.
About 1.9% ($4.706 billion) of Microsoft's FY 2024 revenue was from devices "including Surface, HoloLens, and PC accessories" (and not including Xbox hardware).
About 9.5% ($23.244 billion) was from Windows "including Windows OEM licensing and other non-volume licensing of the Windows operating system; Windows Commercial, comprising volume licensing of the Windows operating system, Windows cloud services, and other Windows commercial offerings; patent licensing; and Windows Internet of Things."
Compared to FY 2023, devices revenue decreased 15% and Windows revenue increased 8%.
