>The TTY sequences to insert or move lines give all the information needed to avoid scrolling other parts of the screen.

Certainly for VT100 they do not - you can define the scroll region, but it's strictly "between line x and y" or "the whole screen" and you can only scroll up/down the entire region.

The article only address smooth scrolling of entire lines. How do you "scroll only the buffer on the right side of the screen"?