In case of this particular interaction its just easy to notice because you have direct view of pen position and what it is drawing so any latency means the pen is dragging but there is nothing under it.

It's different for where you don't have same senses for both. "Pressing" a key is feeling + sound but reaction is change in image, you don't see keyboard and screen at same time so it feels more tolerable.

> "Pressing" a key is feeling + sound but reaction is change in image, you don't see keyboard and screen at same time so it feels more tolerable.

It's not really more tolerable, unless you never experienced low latency here, and your brain is used to the effect of a key press being perceptually immediate.