The demonstrator definitely was unfamiliar with the lathe.
I have a DVR. When it is powered off (the toggle switch on the left end) it will then default to 500 rpm.
When it has powered, whatever speed it is set to will display on the readout. If you then hit the "ON" microswitch, it will spin up to this speed.
Seems the demonstrator hit the "OFF" microswitch and did not adjust the speed before hitting the "ON" microswitch again.
As you observed the DVR is not fast to respond to speed changes when running.
I do not know why NOVA chose 500 rpm as the default, but it is only re-set to this after power off, not microswitch off.
I expect that if all lathe's had some type of electronic control, they could be designed to start at 0 rpm. Have to decide whether this is after power on, or microswitch on.
If every time you started the motor you had to do something to make the lathe rotate, I could imagine people wanting to by-pass this safety design.
I have a buddy who has by-passed his safety belt warning so that he can drive without the safety belt. Just an example that people can dislike safety devices which may be in their best interests.
I attended a bowl turning demo earlier in the year and was glad that I was at the back. Some of the steps looked a bit too risky for me.
Good job no-one was hurt. I bet lots of people were surprised.