So it wasn't just my imagination that installers became faster when doing that...
At 40 this behavior is ingrained in me and influences my behavior while using a computer to this day.
Back in the early 00s my cousin had a modem that would only transfer data if either the mouse or the keyboard was in use.
Wow, I've never heard anyone else describe that.. but I had the same on Win95 (iirc) after messing about with the COM port setup too much. You could try to load a website and see there was no transmission going on whatsoever.. but then if you grabbed the mouse and moved it around you would instantly see data transfer happening again and the page would start to load.