No, you're right, but the fact that Stallman is 70, and "under chemo," and still giving talks would suggest that whatever chemo he's under is relatively easy on his body.
But yes, when I spoke to radiation oncologist when I was diagnosed 2.5 years ago (and before they had a full picture of what my cancer looked like), he told me to expect to be hospitalized multiple times because the lymph nodes they'd treat were so close to my esophagus and the treatments would burn my espohagus. "Thankfully" the cancer was spread too far and the field was too large for radiation, so the only radiation treatments I've had have been the ones described above.
More info on the different kinds of Stereotactic Radiosurgery: https://www.mayoclinic.org/tests-procedures/stereotactic-rad...
When I did chemo, I had cycles with 5 days on - and I couldn't do anything useful during that week, or most of the next week. It was, truly, an awful experience. I completely understand and respect how some people can decide treatment isn't worth it and surrender to the disease.