Not much. I would say that a flow state happens on purpose for something you want to do, and you can easily stop your flow even though it may be difficult to get it started again. With Hyper focus it may happen to something you don't want it to, and you can't easily stop. In the moment it is hard to tell the difference, at least when it's something you want to do.

For example, I was late to an event for my child the other day because I was trying to improve the speed of a one time copy of data from an old computer to a new one. To the point that when I finally pulled myself away, after receiving multiple phone calls, it had been hours and the original method would have been finished if I had just let it run. I felt like I was being productive, but I was not. Once I realized I was wasting my time it took me two more hours to stop.

An example of a bad flow state is I’ll get locked in a Wikipedia hole. It might start on reading up on a topic I need for work (e.g. a class of algorithms), and then next thing I know I’m 6 degrees away from the topic I was supposed to be studying reading about a 16th century battle or whatever.