You could actually get a full desktop experience from a tablet back in 2003, with products like the NEC Versa Litepad [1] running Windows XP. With a fully-fledged x86 processor, you could run anything a desktop could run.
It was pretty neat, but I can tell you from experience that coding using handwriting recognition isn't a great experience :)
[1] https://www.cnet.com/reviews/nec-versa-litepad-tablet-pc-vlp...