He designed a system that, to this day, is still more in the realm of science than engineering. Systems are full of nth-order effects that have to be discovered and worked around in some practical way.
From what I've read of the Autodesk days, he wasn't even on site. Whether he's a programmer or not is immaterial. You've got to birth your own baby. That's just how it works.
When I first met Ted, ca. 1991 or 1992, he was indeed doing most of the Xanadu work on his houseboat in Sausalito. But Autodesk was also in Sausalito, just down the road, so Ted was definitely in the neighborhood, if not exactly in the building.
There was some amount of coding happening at the houseboat, though I have a vague recollection (which may be wrong) that Roger Gregory might have done much of his work offsite -- at his house? -- and then come to the houseboat for meetings.
I saw Ted perhaps a year later and it was definitely in his office at the Autodesk facility. He had quite a nice lab there, and an assistant.
From what I've read of the Autodesk days, he wasn't even on site. Whether he's a programmer or not is immaterial. You've got to birth your own baby. That's just how it works.