The first demonstrator here is Timothy E. Johnson, not Ivan Sutherland. Johnson did the "Sketchpad III" work extending Sketchpad into 3D which is demonstrated from 11:30 https://www.youtube.com/watch?v=6orsmFndx_o&t=690s . Then Larry Roberts appears to demonstrate his own work on hidden-line removal, which is shown from 14:42 https://youtu.be/6orsmFndx_o?t=882 .

See https://tx-2.github.io/videos#sketchpad for more video, including appearances by Sutherland himself. https://tx-2.github.io/ is an active effort to get Sketchpad running again on a new TX-2 emulator.