I'll have to do some A-B testing.

The key here is that I've integrated this particular type of graph as part of a larger interactive visualization or UI. Within that larger system, the graph is generated in real-time in direct response to your input about your own behavior.

I put up an interactive demo here: https://benome.ca/Intro/

So in the intended context, graph's meaning is more clear than it appears at first glance. But in any case, it's easy enough to switch a graph's direction.