I see your point, but actually wouldn't both work? A pie is a circle, while a circumference which is the outline of one is determined by pi and the diameter. Please don't dislike because of this, but I am just saying it is not completely illogical for one to call it a pi chart rather than a pie chart. If you go to the bottom you will see I called it a pie chart in my thank you comment, but everyone knows what it was called in like second grade geometry. So yeah.
