It could have been fed videos of people painting.

Connecting it's capabilities to simulating the recreation of such paintings... that's I suppose interesting. But adding brush strokes to produce an image is probably well covered by video footage in its training data. e.g. all the Bob Ross videos in existence.

The transformation of pixel video data to actual brush strokes is not trivial.

For example I can watch all bob Ross videos 300 times and never paint a thing and this action would not teach me how to paint.