Pollock is an odd target here in a way, because the man was actually skilled, he produced things which proved hard to copy. Unlike a lot of later very-abstract artists, who really were all about their timing / positioning / contacts etc.

I would have to google a lot but there was a nice mathematical investigation of this, in which the summary was something like that he produced a very consistent scaling of details from very small to quite large, in a way which matches natural scenes. Whereas fake Pollocks don't show this, and perhaps that is why they aren't as pleasing.