Well, the author needs it to be a tablet form factor with a stylus as described here https://teddysvoronos.com/2015-11-19-in-praise-of-goodnotes/

Both the hardware and software market for tablets running a real desktop OS still seem pretty terrible, and it's been over 10 years since the release of the first Apple Pencil. No competition seems to be coming at all. Windows Surface exists, but software is still not great and the stylus not as good as Apple's.